When you’re craving comfort food but need to keep carbs in check, this keto broccoli cauliflower au gratin with sausage delivers exactly what you need. Tender vegetables get smothered in a rich, creamy cheese sauce with savory sausage throughout, creating a dinner that’s both satisfying and completely low-carb friendly. The golden, bubbling top straight from the oven looks impressive enough for company but comes together easily enough for a regular weeknight.
What makes this dish particularly smart is how it transforms vegetables that might otherwise be side dishes into a complete, protein-rich main course. The smoked sausage adds smoky, savory depth and makes the meal genuinely filling, while the cream cheese and cheddar sauce creates that indulgent au gratin texture without any flour or breadcrumbs. At just 8 grams of carbs per serving with 3 grams of fiber, this fits perfectly into keto macros while tasting like you’re cheating.
Why You’ll Love This Keto Broccoli Cauliflower Au Gratin
This recipe solves one of the biggest challenges of keto cooking: making vegetable dishes that feel substantial enough to serve as dinner rather than just a side. The combination of broccoli and cauliflower provides bulk and nutrition, while the sausage adds protein and fat that keep you satisfied for hours. The cheese sauce is where the magic happens—creamy, rich, and coating every piece of vegetable and sausage.
The cooking method is straightforward with just two components to prepare before assembling. Brown the sausage to develop flavor and render some fat, then make a simple cheese sauce that comes together in one pan. Everything gets tossed together and baked until bubbly and golden. The total time is just 40 minutes, with most of that being hands-off baking.
The flavor profile hits all the right notes for comfort food. The smoked sausage provides a savory, slightly smoky base, while the onions and garlic in the sauce add aromatic depth. Cheddar cheese brings sharp, tangy flavor, and the cream cheese creates silky texture. The vegetables themselves offer mild sweetness and different textures—cauliflower is tender and almost creamy when baked, while broccoli maintains a slight firmness.
At 500 calories per serving with 20 grams of protein and 45 grams of fat, this provides the high-fat, moderate-protein ratio that keto diets require. The meal prep potential is outstanding—this freezes beautifully and reheats without losing quality, making it perfect for batch cooking.
Ingredients for Easy Keto Broccoli & Cauliflower Au Gratin with Sausage
I keep most of these ingredients on hand because they’re keto staples that work in countless low-carb recipes. The only items you might need to specifically shop for are the fresh vegetables if you don’t typically stock them.
Veggies:
- 1 head cauliflower, cut into florets
- 1 head broccoli, cut into florets
Sausage:
- 12 oz smoked sausage, sliced into rounds
Cheese Sauce:
- 2 tablespoons butter
- 1 medium onion, finely diced
- 2 garlic cloves, minced
- 8 oz cream cheese, softened
- 1 cup heavy cream
- 2 cups shredded cheddar cheese
- Salt and freshly ground black pepper, to taste
About the Vegetables: One head each of broccoli and cauliflower yields about 4-5 cups of florets total, which is the perfect amount for this recipe. Cut them into bite-sized pieces, roughly 1-1.5 inches. Pre-chopped bags of florets save time and work perfectly if you’re short on prep time. The broccoli should be briefly steamed or blanched—just 4-6 minutes until bright green and slightly tender. Don’t skip this step; raw broccoli won’t cook through properly during baking. The cauliflower can go in raw since it softens more quickly.
Choosing Your Sausage: Smoked sausage (like kielbasa-style) is my preference because it adds deep, smoky flavor without being spicy. Look for varieties that are 12-14 ounces. Slice it into rounds about 1/4 inch thick. Andouille sausage creates a Cajun-inspired version with more heat, while Italian sausage adds fennel and herb notes. Check the ingredient list to ensure your sausage doesn’t contain added sugars or fillers that increase carb counts—most smoked sausages are naturally keto-friendly, but it’s worth verifying.
The Cheese Components: Softened cream cheese is crucial—take it out of the refrigerator 30-60 minutes before cooking so it melts smoothly into the sauce without lumps. If you forget, cut it into small cubes to help it melt faster. For the cheddar, I always use freshly shredded cheese from a block rather than pre-shredded. Pre-shredded cheese contains anti-caking agents that prevent it from melting as smoothly and can make the sauce grainy. Sharp cheddar provides the best flavor, though medium or mild work if you prefer less tang.
Heavy Cream Matters: Full-fat heavy cream is essential for keto cooking and creates the luxurious texture you want in this sauce. Don’t substitute half-and-half or milk—they won’t provide the proper fat content or richness, and they’re higher in carbs.
How to Make Keto Broccoli Cauliflower Au Gratin with Sausage
This recipe builds flavor through simple steps that layer taste and texture. Nothing here is complicated, but each element contributes to the final result.
Prep and Brown the Sausage
Preheat your oven to 350°F and grease a 9×9-inch baking dish with butter or cooking spray. Slice your smoked sausage into rounds about 1/4 inch thick. Heat a large skillet over medium-high heat—no oil needed since the sausage will release its own fat. Add the sausage slices in a single layer and let them cook undisturbed for 2-3 minutes until the bottoms develop golden-brown spots. Flip and cook another 2-3 minutes until both sides have color and the edges get slightly crispy.
This browning step is important. It creates texture contrast in the final dish and develops deeper flavor through caramelization. The rendered fat that comes out also adds savory richness to the skillet, which will flavor your onions in the next step if you choose to use the same pan. Once browned, transfer the sausage to a plate and set aside.
Make the Cheese Sauce
In a medium saucepan (or the same skillet after removing the sausage), melt the butter over medium heat. Add the finely diced onion and cook for 3-4 minutes, stirring occasionally, until it softens and becomes translucent. The onion should smell sweet and aromatic, not raw. Add the minced garlic and stir constantly for 30 seconds until fragrant. Watch the garlic carefully—burned garlic tastes bitter.
Reduce the heat to medium-low and add the softened cream cheese in chunks. Stir continuously as it melts into the onions and butter, breaking up any lumps with your spoon. Once the cream cheese is mostly melted and smooth, slowly pour in the heavy cream while whisking. The sauce will thin out at first, then gradually thicken as it heats. Let it simmer gently for 3-5 minutes, whisking occasionally, until it’s thick enough to coat the back of a spoon.
Remove the pan from the heat and add the shredded cheddar cheese in handfuls, stirring after each addition until it melts completely before adding more. Working off the heat prevents the cheese from becoming stringy or grainy. Once all the cheese is melted and the sauce is smooth, taste it and season with salt and pepper. Remember that the sausage is already salty, so start with less salt than you think you need.
Combine and Bake
In a large mixing bowl, combine your broccoli florets (steamed and patted dry), cauliflower florets, and browned sausage. Pour the cheese sauce over everything and use a large spoon or spatula to toss gently until every piece is coated in sauce. The vegetables should be well-covered but not swimming in excess liquid.
Transfer the mixture to your prepared baking dish, spreading it into an even layer. Make sure to scrape out all the sauce from the bowl—you want every bit of that cheesy goodness. Slide the dish into your preheated oven and bake for 15-20 minutes until the casserole is bubbling around the edges and the top develops a light golden color. You’ll see the cheese sauce bubbling up through the vegetables when it’s ready.
If you want extra browning and a slightly crispy top, switch your oven to broil for the last 1-2 minutes. Watch it closely during broiling—the difference between perfectly browned and burned happens quickly. Remove from the oven and let rest for 5 minutes before serving. This resting time allows the sauce to thicken slightly and makes serving much easier.
What to Serve with Keto Broccoli Cauliflower Au Gratin
Since this dish is already quite complete with protein, vegetables, and plenty of fat, I focus on simple, fresh sides that add variety without making the meal too heavy.
Crisp Green Salad: A simple salad with mixed greens, cucumber, radishes, and a tangy vinaigrette provides freshness and crunch. The acidity cuts through the rich cheese sauce and refreshes your palate.
Garlic Parmesan Zucchini Noodles: Spiralized zucchini quickly sautéed with garlic, butter, and Parmesan offers a pasta-like element without the carbs. The mild zucchini complements the bold flavors of the au gratin.
Roasted Asparagus: Asparagus spears roasted with olive oil, salt, and a squeeze of lemon add elegance and a slight bitter note that balances the richness. The tender-crisp texture provides nice contrast.
Bacon-Wrapped Avocado Slices: For an extra-indulgent keto meal, bacon-wrapped avocado brings healthy fats and a smoky element. The creamy avocado mirrors the richness of the cheese sauce.
Cauliflower Rice Pilaf: If you want more bulk, cauliflower rice sautéed with butter, herbs, and a touch of chicken broth provides a neutral base similar to regular rice.
Simple Cucumber Salad: Thinly sliced cucumbers marinated in vinegar with dill and a pinch of sweetener offer cooling, refreshing contrast. The acidity and crunch balance the creamy main dish.
Pro Tips & Variations
Prevent Watery Sauce: The biggest mistake is not properly draining the vegetables. After steaming the broccoli, spread it on paper towels and pat completely dry. Any excess moisture will dilute your cheese sauce and make the dish watery. Similarly, if your cauliflower releases water during baking, the pre-baking step of tossing everything together helps identify if you need to drain anything before it goes in the oven.
Texture on Top: For added crunch, sprinkle crushed pork rinds or toasted almond slices over the top before baking. The pork rinds create a breadcrumb-like texture that’s completely carb-free. Toast slivered almonds in a dry skillet until golden for a nutty, crunchy topping.
Spice It Up: Red pepper flakes stirred into the cheese sauce or a pinch of cayenne adds pleasant heat that cuts through the richness. If using andouille sausage, you might not need additional spice since it’s already quite bold.
Cheese Variations: Gruyère instead of cheddar creates a more sophisticated, nutty flavor profile reminiscent of classic French gratins. Fontina melts beautifully and offers mild, buttery taste. A combination of sharp cheddar and smoked gouda brings depth and smokiness that complements the sausage.
Vegetarian Option: Omit the sausage entirely and add sautéed mushrooms, which provide umami and a meaty texture. Marinated artichoke hearts bring tangy flavor and interesting texture. You might want to add an extra ounce of cream cheese to compensate for the fat from the missing sausage.
Make It a Complete Meal: Add diced cooked bacon to the vegetable mixture for extra protein and smoky flavor. Chopped hard-boiled eggs folded in before baking add protein and create a heartier dish.
Storage & Reheating Tips
I store leftover au gratin in an airtight container in the refrigerator for up to 3 days. The cheese sauce thickens as it cools, which actually makes leftovers easier to portion and reheat. If the sauce seems too thick after refrigeration, stir in a tablespoon of heavy cream before reheating to loosen it.
For reheating, the oven method produces the best results. Place portions in an oven-safe dish, cover with foil, and heat at 350°F for 15-20 minutes until warmed through. Remove the foil for the last 5 minutes to crisp up the top. The microwave works for quick reheating—heat on medium power for 2-3 minutes, stirring halfway through. The cheese might separate slightly in the microwave but will come back together when stirred.
This recipe is excellent for meal prep and freezes beautifully for up to 2 months. Let the casserole cool completely before freezing to minimize ice crystals. I prefer freezing individual portions in meal-prep containers rather than the entire dish—it thaws faster and you can grab single servings as needed. Thaw overnight in the refrigerator before reheating. You can also reheat from frozen; just add an extra 10-15 minutes to the baking time and keep it covered with foil.
For baking in small ramekins for individual servings, divide the mixture among 4-6 ramekins and reduce baking time to 12-15 minutes. These freeze particularly well and make grab-and-go meals convenient.
Common Questions
How many net carbs per serving? Each serving contains 8 grams of total carbs with 3 grams of fiber, giving you 5 net carbs per serving. This fits comfortably into most keto meal plans, which typically allow 20-30 net carbs per day.
Can I use frozen vegetables? Yes, but thaw them completely first and squeeze out as much moisture as possible. Frozen vegetables contain more water than fresh, so if you don’t drain them thoroughly, your sauce will be watery. I prefer fresh or fresh-frozen florets for the best texture.
What if my cheese sauce is grainy? This usually happens when the cheese is added at too high a temperature or heated too much after adding. Always remove the pan from heat before stirring in the shredded cheese, and never let the sauce boil once cheese is added. If it does become grainy, sometimes whisking vigorously off the heat can bring it back together.
Can I prep this ahead for a dinner party? Absolutely. Assemble everything up to the baking step, cover tightly with plastic wrap or foil, and refrigerate for up to 24 hours. Let it sit at room temperature for 20 minutes before baking, then add 5-10 extra minutes to the baking time since it’s starting cold.
Is this diabetic-friendly? Yes, when portion-controlled. The low carb count and high fat/protein content help prevent blood sugar spikes. However, individuals should consult their healthcare provider about how this fits into their specific dietary plan, as needs vary.
This keto broccoli cauliflower au gratin with sausage proves that low-carb eating doesn’t mean giving up comfort food. The creamy cheese sauce, tender vegetables, and savory sausage create a dinner that satisfies cravings while keeping you on track with your keto goals. Whether you’re feeding the family or meal prepping for the week, this recipe delivers every time.
Easy Keto Broccoli & Cauliflower Au Gratin with Sausage
Ingredients
Equipment
Method
- Preheat oven to 350°F (175°C) and grease a 9×9-inch baking dish. Steam broccoli florets for 4-6 minutes until bright green and slightly tender. Pat completely dry with paper towels.
- In a large skillet over medium-high heat, brown sausage slices for 5-7 minutes until golden with crispy edges. Transfer to a plate and set aside.
- In a medium saucepan, melt butter over medium heat. Add diced onion and cook for 3-4 minutes until softened and translucent. Stir in minced garlic and cook 30 seconds until fragrant.
- Lower heat to medium-low. Add softened cream cheese in chunks, stirring continuously until melted and smooth. Slowly whisk in heavy cream and simmer for 3-5 minutes, whisking occasionally, until sauce thickens enough to coat the back of a spoon.
- Remove pan from heat. Add shredded cheddar cheese in handfuls, stirring after each addition until completely melted before adding more. Season with salt and pepper to taste, keeping in mind the sausage is already salty.
- In a large bowl, combine steamed broccoli, cauliflower florets, and browned sausage. Pour cheese sauce over the mixture and toss gently until everything is evenly coated.
- Transfer to prepared baking dish and spread into an even layer. Bake for 15-20 minutes until bubbling around the edges and lightly golden on top. For extra browning, broil for 1-2 minutes, watching closely.
- Let rest for 5 minutes before serving. The sauce will thicken slightly during resting.
