Combine tomato paste and mustard in a small bowl. Set aside.
Place meatloaves back in the oven. Bake muffins for about 25 more minutes. Ensure these are cooked through before removing from the oven.
Place individual meatloaf muffins on a serving dish.
In an icing piping bag, insert a icing tip with a large opening. Fill bag with mashed potatoes (see recipe linked in post).