Preheat oven to 375°F (190°C). Grease a 9x13-inch casserole dish.
In a large bowl, combine ground beef, onion, garlic, breadcrumbs, eggs, ketchup, Worcestershire sauce, salt, and pepper. Mix gently until just combined.
Press mixture evenly into the prepared dish. Bake for 25–30 minutes until browned and cooked through. Drain excess fat.
While meatloaf bakes, boil potatoes in salted water until tender (about 15–20 minutes). Drain, then mash with butter, sour cream, milk, garlic powder, salt, and pepper until smooth.
Spread mashed potatoes evenly over the baked meatloaf layer.
Sprinkle cheddar cheese, bacon crumbles, green onions, and chives on top.
Return casserole to oven and bake for an additional 15–20 minutes, until cheese is melted and bubbly.
Let cool for 10 minutes before slicing and serving hot.
