Soak the rolls in cold water for about 5 minutes. In the meantime wash parsley, dab dry, pluck leaves from the stalks and chop finely. Peel onion and chop finely. Mix the minced meat with the well squeezed bread roll, egg, parsley and onion.
Season with salt and pepper. Form 4 medium-sized meatballs with moistened hands. Heat oil in a pan and fry the meatballs in it at medium heat while turning for about 10 minutes. Remove the meatballs and let them cool down.
Cut mozzarella and olives in half crosswise. Place 2 half mozzarella balls and 2 half olives as eyes on each meatball. Paint mouths with ketchup as desired. Arrange the meatballs on a plate with some salad leaves.