Heat oven to 375°F (190°C) and grease a muffin tin.
Combine beef, breadcrumbs, milk, egg, ¼ cup ketchup, Worcestershire sauce, garlic powder, onion powder, salt, and pepper until just blended.
Divide mixture evenly into muffin cups, press lightly, and top with remaining ketchup.
Cook for 20–25 minutes until browned and cooked through.
Warm mashed potatoes with butter and milk until smooth and fluffy.
Let muffins rest for 5 minutes, then pipe mashed potatoes on top like frosting.
Garnish with parsley and serve warm.
