Prepare the Meatloaf: Preheat oven to 375°F (190°C) and grease a 9×13-inch baking dish. In a large bowl, mix ground beef, breadcrumbs, egg, milk, salt, pepper, garlic powder, onion powder, Worcestershire sauce, and ketchup. Press the mixture evenly into the prepared baking dish. Bake for 20 minutes.

Prepare the Mashed Potatoes: While the meatloaf bakes, boil the cubed potatoes in salted water until tender, about 15 minutes. Drain and mash with butter, sour cream, milk, salt, and pepper. Stir in shredded cheddar cheese.

Assemble and Bake: Spread the mashed potatoes evenly over the partially baked meatloaf. Sprinkle the top with crumbled bacon, green onions, and extra cheddar cheese. Return to the oven and bake for another 15-20 minutes, until the cheese is melted and bubbly.

Serve: Let cool for 5 minutes before slicing. Serve warm and enjoy.