Preheat oven to 375°F (190°C). Line a muffin tin with foil liners or spray well.
Mix breadcrumbs and milk in a bowl and let sit 1 minute. Add beef, egg, onion, garlic, ketchup, Worcestershire, salt, pepper, and veg if using.
Combine gently with your hands or a spoon until just mixed. Divide into 6 portions and press into muffin cups.
Spoon a little ketchup on each mini meatloaf for a glaze. Bake 18–22 minutes until cooked through.
Cool, wrap individually, and freeze flat. Reheat covered in microwave or oven until hot.