Soak rolls in cold water. Peel and finely chop the onion. Squeeze the bread well. Put minced meat, onion, egg and roll in a bowl. Season with mustard, salt and pepper and mix everything well.
Form about 16 meatballs with wet hands. Clean and wash the mushrooms and chanterelles and pat them dry well. Depending on the size, possibly halve them. Clean, wash and cut the leek into rings. Heat the oil in a pan and fry the meatballs all around, turning them over. Take them out and fry the mushrooms in the hot frying fat as well. Finally add leek and braise. Deglaze with broth. Stir in crème-fraîche and sauce thickener and season with salt and pepper. Bring everything to the boil once and place in an ovenproof dish together with the meatballs.
Finally add leek and braise. Deglaze with broth. Stir in crème-fraîche and sauce thickener and season with salt and pepper. Bring everything to the boil once and place in an ovenproof dish together with the meatballs. Cover and braise in the preheated oven (electric cooker: 200°C/ gas: level 3) for another 15-20 minutes. In the meantime wash parsley, dab dry and chop. Sprinkle over the vegetables and serve immediately