Mix the minced meat with the egg, onions, garlic and yoghurt to a malleable meat dough. If the dough is too soft, add a small handful of breadcrumbs. Season to taste with salt and pepper, form small balls out of the meat dough and let simmer in gently simmering salted water for 15-20 minutes, but do not boil!
Prepare a roux for the butter and flour sauce and deglaze the balls with about 3/8 liter of the meat stock and let it boil a little. Roughly grate the apple and add to the sauce with the cream. Then season the sauce with sugar, salt and curry to taste. Serve the balls in the sauce.