Wash the tomatoes and cut off one lid each. Hollow out the tomatoes (use the inside for other purposes). Boil 3/4 l water and salt. Remove from heat, add milk and puree. Wash parsley and chop finely, except for a little bit. Stir butter and half of the parsley into the puree, season with nutmeg. Fill the tomatoes with the puree up to half each. Spread the rest of the puree into a greased casserole dish
Form 4 meatballs from the mince and fill them into the tomatoes. Add the tomatoes to the puree. Bake everything covered with aluminium foil in a hot oven (electric cooker: 200 °C/circulating air: 175 °C/gas: level 3) for 35-40 minutes
Drain the mozzarella and cut into slices. Remove aluminium foil after half the baking time. Place the cheese on the tomatoes, put the lids on them and drizzle with oil. Bake open to the end. Sprinkle with rest of parsley and garnish