Preheat oven to 375°F (190°C). Lightly grease a 9x13-inch baking dish.
In a large bowl, mix ground beef, onion, garlic, breadcrumbs, ketchup, eggs, Worcestershire sauce, salt, and pepper until well combined.
Press meat mixture evenly into the bottom of the baking dish.
Bake for 25-30 minutes or until the meat is fully cooked.
Remove from oven and spread mashed potatoes over the meat layer.
Sprinkle cheddar cheese and bacon bits evenly on top.
Return to oven and bake for another 10-15 minutes, until cheese is melted and bubbly.
Top with chopped green onions and serve warm.