Chop the onion and garlic very finely (e.g. in the moulinette). Core the chilli pepper (if no chilli pepper is available, cayenne pepper can be used) and finely chop. Mix the minced meat with the egg, onions, garlic (more if you like) and the remaining ingredients to a dough by hand, season well with salt and pepper. Chill for 1-2 hours and let it steep. Then knead again briefly.
For the filling, finely mash the feta with a fork on a plate. Finely chop the drained pitted olives. Mix the feta, olives, oregano and tzatziki (only the sauce) into a mass.
With moistened hands, remove portions from the minced meat mixture, press flat, remove a small portion of the cheese mixture with a teaspoon and fill the meatball with it, close carefully. The layer of minced meat around the filling should not be too thin, otherwise the mixture can run out during frying, which of course it shouldn`t.
Fry both sides in a little olive oil.
Serve with tzatziki.
This goes well with tomato rice and eggplant vegetables.
Remnants of the filling can be mixed with cream cheese to make a spread.