Step 1: Prepare the Meatloaf Base

1. Preheat your oven to 375°F (190°C). Lightly grease a 9×13-inch baking dish or casserole dish.
2. In a large mixing bowl, combine the ground beef, chopped onion, breadcrumbs, milk, egg, ketchup, Worcestershire sauce, garlic powder, onion powder, paprika, salt, and pepper. Mix until just combined.
3. Press the meatloaf mixture evenly into the prepared baking dish, creating a flat, uniform layer.

Step 2: Bake the Meatloaf

1. Bake the meatloaf base in the preheated oven for 25 minutes. Remove from the oven but do not turn off the heat.

Step 3: Prepare the Loaded Mashed Potatoes

1. While the meatloaf is baking, prepare the mashed potatoes if you haven’t already. Peel, dice, and boil the potatoes until fork-tender. Drain well.
2. Mash the potatoes with sour cream, melted butter, cheddar cheese, bacon, green onions, salt, and pepper. Adjust seasoning to taste.

Step 4: Assemble the Casserole

1. Spread the mashed potato mixture evenly over the partially baked meatloaf base. Use a spatula to smooth the top.
2. Sprinkle the additional cheddar cheese and crumbled bacon over the potato layer.

Step 5: Bake the Casserole

1. Return the casserole to the oven and bake for an additional 20–25 minutes, or until the cheese is melted and bubbly.
2. If desired, broil for 2–3 minutes to achieve a golden-brown crust on the cheese.

Step 6: Garnish and Serve

1. Remove the casserole from the oven and let it rest for 5–10 minutes.
2. Garnish with fresh parsley or additional green onions before serving.