Step 1

Preheat oven to 375 degrees. Spray a 12-cup muffin pan with nonstick spray.

Step 2

In a large bowl, thoroughly mix beef, mushrooms, seasoning mix, egg whites/substitute, breadcrumbs, garlic powder, and pepper.

Step 3

Evenly transfer to muffin pan, and smooth out the tops. Bake until firm with lightly browned edges, about 35 minutes.

Step 4

Meanwhile, melt butter in a large skillet over medium-low heat. Add onions, and cook and stir for 15 minutes.

Step 5

Add chopped garlic, and cook and stir until garlic is fragrant and onions have caramelized, about 3 more minutes.

Step 6

Evenly spoon onions over meatloaves and top with cheese. Bake until melted, about 3 minutes.