Preheat oven to 400°F (200°C). Cut the top quarter-inch off a head of garlic to expose the cloves. Place on aluminum foil, drizzle with 2 tablespoons olive oil, and wrap completely. Roast for 30-35 minutes until cloves are soft and golden. Set aside to cool slightly.

Slice Yukon Gold potatoes into ¼-inch rounds using a mandoline or sharp knife. Place slices in a large bowl of cold water and soak for 30 minutes to remove excess starch.

Drain potatoes thoroughly and pat completely dry with clean kitchen towels. Any remaining water will dilute the sauce.

Squeeze roasted garlic cloves from their skins into a small bowl and mash with a fork until relatively smooth.

In a medium saucepan over medium-low heat, combine heavy cream, melted butter, and mashed roasted garlic. Add grated Parmesan, smoked paprika, dried thyme, dried rosemary, kosher salt, and black pepper. Stir continuously for 5-7 minutes until sauce thickens and coats the back of a spoon. Remove from heat.

Grease a 9x13-inch baking dish or 6 individual ramekins with butter. Begin layering by placing a potato slice at the bottom, then spooning about 1 tablespoon of sauce over it. Add another potato slice, then more sauce. Continue until you've created stacks of 8-10 slices each. Reserve some sauce for drizzling on tops.

Cover the baking dish tightly with aluminum foil. Bake at 400°F for 40 minutes until potatoes are tender when pierced with a knife.

Remove foil and drizzle remaining sauce over the tops of the stacks. Return to oven uncovered and bake for an additional 10-15 minutes until tops are golden brown with slightly crispy edges.

Remove from oven and let rest for 5 minutes to allow sauce to set and layers to firm up. Garnish with freshly chopped parsley just before serving.