Preheat the Oven: Start by preheating your oven to 375°F (190°C).
Mix the Meatloaf Base: In a large bowl, combine the ground beef, breadcrumbs, egg, milk, ketchup, garlic powder, onion powder, salt, and pepper. Mix until just combined.
Shape and Bake: Press the meat mixture into the bottom of the baking dish, spreading it evenly. Bake for 20 minutes.
Prepare the Mashed Potatoes: While the meatloaf base bakes, prepare mashed potatoes if you haven’t already. Use store-bought or homemade, seasoned with butter and salt.
Layer the Casserole: Remove the dish from the oven and spread the mashed potatoes over the meatloaf base.
Add Cheese and Bacon: Sprinkle shredded cheddar cheese and bacon bits evenly over the mashed potatoes.
Final Bake: Return the dish to the oven and bake uncovered for another 15-20 minutes until the cheese is melted and bubbly.
Garnish and Serve: Optional—sprinkle with chopped green onions before serving.