Soak rolls in water. Peel and finely dice onions. Drain tomatoes and dice finely. Chop olives. Squeeze the bread rolls vigorously. Put ground pork fat, minced meat, rolls, herbs, onions, tomatoes, olives, eggs, mustard, salt and pepper in a bowl and knead well.
Shape into about 30 small meatballs with wet hands. Brush a baking tray thinly with oil, place the meatballs on top and bake in a preheated oven (electric cooker: 200 °C/ convection oven: 175 °C/ gas: level 3) for approx. 25 minutes.
Wash the tomatoes. Put a mozzarella ball and a cherry tomato on 30 skewers each. Take the meatballs out of the oven, put one skewer on each and arrange them in small bowls.