Preheat your oven to 375°F (190°C).
In a large skillet, sauté the diced onions until translucent and fragrant, about 5 minutes.
In a large bowl, combine ground beef, sautéed onions, breadcrumbs, garlic, eggs, salt, pepper, paprika, milk, and sour cream.
In a greased 9x13 inch baking dish, distribute the meat mixture evenly.
In a separate bowl, combine the diced potatoes with remaining milk, sour cream, and half of the cheddar cheese. Mix well.
Spread the potato mixture over the meatloaf in the baking dish, evening out the surface with a spatula.
Sprinkle the remaining cheddar cheese on top of the potato layer.
Bake in the preheated oven for 1 hour or until the internal temperature reaches 160°F (70°C).
Let the casserole rest for 10 minutes before serving.
