Preheat Oven
Preheat oven to 375°F (190°C). Lightly grease a 9×13-inch baking dish.
Make Meatloaf Base
In a large bowl, combine ground beef, breadcrumbs, eggs, milk, onion, garlic, salt, and pepper. Mix gently until just combined.
Assemble Base Layer
Press the meat mixture evenly into the bottom of the prepared baking dish.
Add Potato Layer
Mix mashed potatoes with sour cream and butter. Spread evenly over the meatloaf layer.
Top with Cheese
Sprinkle shredded cheddar cheese evenly over the potatoes.
Bake
Bake uncovered for 40 minutes, or until meat is cooked through and cheese is melted and bubbly.
Rest & Serve
Let rest for 10 minutes before slicing and serving.