Soak the rolls and squeeze them well. Sauté the onion cubes until translucent. Put all ingredients, except for the feta, in a bowl and mix well. Divide the feta into 8 pieces. Then shape 8 meatballs and press a piece of feta in the middle of each. The cheese must be completely enclosed by the meat. Now fry the meatballs in a hot pan. The whole thing is also possible on the grill in summer.