Preheat the oven to 350°F (175°C).
Peel and dice the potatoes into cubes.
Boil the potatoes in salted water until fork-tender, about 15-20 minutes.
While the potatoes cook, sauté the diced onion and minced garlic until translucent.
In a large bowl, combine ground beef, sautéed onion and garlic, breadcrumbs, egg, Worcestershire sauce, salt, and pepper.
Form the ground beef mixture into a loaf and place it in a greased baking dish.
Bake the meatloaf in the preheated oven for 30-35 minutes.
While the meatloaf bakes, drain the potatoes and mash them with sour cream, salt, and pepper.
Once the meatloaf is cooked, spread a layer of mashed potatoes on top.
Sprinkle shredded cheddar cheese over the mashed potatoes.
Return the casserole to the oven and bake for an additional 15-20 minutes until cheese is melted and bubbly.
Allow the casserole to rest for a few minutes before serving.