Preheat the oven to a temperature of 375°F. Prepare a 9x13 inch baking pan by spraying it with a nonstick cooking spray.

In a large bowl, combine the ground beef or turkey, chopped white onion, minced garlic, seasoned bread crumbs, Worcestershire sauce, lightly beaten egg, cottage cheese, and BBQ sauce.

Transfer the meat mixture into the prepared baking pan, ensuring it is evenly spread. Bake in the preheated oven for a duration of 30 minutes.

Concurrently, place the diced potatoes in a pan filled with water and cook over medium heat until they are tender.

Once the potatoes are cooked, drain the water and incorporate the unsalted butter. Utilize a hand mixer to achieve a smooth consistency. Subsequently, add the sour cream, warm milk or half-and-half, kosher salt, and ground black pepper. Mix until all ingredients are well-combined.

After the meatloaf has baked for 30 minutes, remove it from the oven and carefully drain any excess grease.

Apply an even layer of the mashed potatoes over the meatloaf. This should be followed by a generous sprinkling of shredded cheddar cheese and crumbled bacon.

Place the casserole back into the oven and bake for an additional 15 minutes. The objective is to ensure that the potatoes are thoroughly heated and the cheese has completely melted.

Once completed, remove the casserole from the oven and let it cool slightly before serving.