Preheat the oven according to the garlic bread package instructions, typically 375°F to 400°F. Place the bread or Texas toast slices on a baking sheet and bake until lightly golden but not fully crisped, about 10 to 12 minutes. The surface should be set and butter melted through, but the edges should still have some give.

While the bread bakes, heat a large skillet over medium-high heat. Add the ground beef and diced onion. Cook, breaking the meat into small crumbles, for 6 to 8 minutes until fully browned and the onion is soft. Drain any excess grease.

Stir in the ketchup, mustard, Worcestershire sauce, garlic powder, salt, and pepper. Add water a tablespoon at a time if the sauce is thicker than desired. Reduce heat to low and simmer for 5 to 7 minutes, stirring occasionally, until the sauce is glossy and coats the beef evenly.

Remove the partially baked garlic bread from the oven. Use the back of a spoon to press a slight well into the center of each slice to cradle the filling.

Spoon the hot Sloppy Joe mixture generously over each slice, spreading toward the edges but leaving a small border of visible garlic bread around the perimeter.

Scatter the shredded cheese evenly over the meat on each slice.

Return the baking sheet to the oven for 5 minutes until the cheese is fully melted and bubbling and the edges of the garlic bread are deep golden and crisp.

Garnish with fresh parsley and serve immediately while the cheese is hot and the bread is at peak crunch.