Preheat oven to 375°F (190°C).
Mix ground beef, eggs, milk, breadcrumbs, onions.
Add garlic, Worcestershire sauce, salt, and pepper.
Press mixture evenly into greased casserole dish.
Bake meatloaf layer for 20 minutes.
Boil potatoes until fork-tender, about 15 minutes.
Drain and mash with butter, salt, and milk.
Spread mashed potatoes over cooked meat layer.
Sprinkle cheese and bacon evenly on top.
Return casserole to oven for 15 more minutes.
Broil 2–3 minutes until cheese is golden.
Top with green onions and serve warm.