1️⃣ Preheat oven to 375°F (190°C). Grease a 9×13 inch casserole dish.
2️⃣ Boil potatoes in salted water for 12–15 minutes until fork-tender. Drain well.
3️⃣ Mash potatoes with butter, sour cream, milk, garlic powder, salt, and pepper. Stir in half of the shredded cheese. Set aside.
4️⃣ In a mixing bowl, combine ground beef, egg, breadcrumbs, milk, onion, garlic, Worcestershire, paprika, chili powder, salt, pepper, and ketchup. Mix just until combined — do not overmix.
5️⃣ Press meatloaf mixture into the bottom of the casserole dish. Spread a thin layer of ketchup on top.
6️⃣ Spread the mashed potatoes evenly over the meat mixture. Top with remaining cheese.
7️⃣ Bake for 45–55 minutes, or until the meatloaf reaches an internal temperature of 160°F (71°C) and the top is slightly golden.
8️⃣ Let rest 5–10 minutes before serving. Garnish with green onions or bacon if desired.