Open can. Separate the dough pieces and spread them on a baking tray lined with baking paper. Cut crosswise with a sharp knife, cover with a clean cloth and let rest for about 30 minutes.
Bake in the preheated oven (electric cooker: 200 °C/ convection oven: 175 °C/ gas: level 3) for 10-15 minutes. For the meatballs peel onion and cut into fine cubes. Knead onion and minced meat and form into 8 flat meatballs.
Wash, clean and cut the tomato into 8 slices. Clean, wash and dry lettuce. Drain mozzarella balls and cut in half. Wash basil, shake dry and pluck leaves from the stalks.
Chop except for something to garnish. Heat the oil in a large frying pan. Fry the meatballs for 6-10 minutes while turning. Cut open finished rolls and cover with lettuce, ketchup, meatballs, tomato and mozzarella.
Garnish with basil.