Combine the minced meat with breadcrumbs, 1 finely chopped onion, salt and pepper. Knead until evenly mixed. Form into small balls and place them in a greased baking dish.
Mix the tomato soup with the cream and pour over the meatballs. Slice the mozzarella and arrange it on top.
Bake uncovered for 40 minutes at 200°C (392°F) until the cheese is melted and the meatballs reach an internal temperature of 71°C (160°F).
Garnish with fresh basil and serve with potatoes or bread.