Set your oven to 375°F (190°C). Grease a baking dish with oil or cooking spray.
In a bowl, mix ground beef, bread crumbs, chopped onions, curry powder, Italian seasoning, egg, garlic, salt, and black pepper. Gradually add milk and mix until cohesive. Form into meatballs (~1.5-inch diameter). Place in baking dish.
Bake meatballs for 30 minutes until cooked through and slightly browned.
In a saucepan, melt margarine. Add chopped onions and cook until golden (~5–7 mins). Stir in ketchup, beef stock, steak sauce, Worcestershire sauce, vinegar, coffee granules, brown sugar, and lemon juice. Bring to a boil, then simmer.
Remove meatballs from oven and drain excess grease. Pour sauce over meatballs and bake again for 30 minutes.
Let cool and rest for enhanced flavor. Reheat at 200°F (93°C) for 15 minutes before serving.
Serve hot with extra sauce spooned over.