Clean, wash and cut the soup vegetables into large pieces. Wash and halve the tomato. Peel and halve 1 onion. Heat the oil in a large pot. Fry the cut surfaces of the onion in it.
Add soup vegetables and tomato, roast with, deglaze with 1 1/2 litres of water. Add bay leaf, 1 1/2 tsp. salt and peppercorns and bring to the boil. Cover and simmer for about 5 minutes.
Wash the meat, dab dry and add to the vegetable stock. Bring to the boil, cover and simmer at low heat for about 30 minutes. Wash parsley, shake dry and chop the leaves. Remove the crusts from white bread, dice the bread coarsely and chop coarsely in the universal chopper.
Mix with cheese and parsley.
Remove the meat from the stock and allow to cool for about 15 minutes. Pour stock through a sieve, collect and measure 300 ml. Use the remaining stock for other purposes. Peel and finely chop 1 onion. Heat 30 g butter in a saucepan, fry onion in it.
Add flour and sweat briefly while stirring. Pour in the stock while stirring and bring to the boil. Simmer at low heat for about 5 minutes. Stir in mustard and crème fraîche, season to taste with salt, pepper and sugar.
Pluck the chicken fillets into large pieces, place in an ovenproof dish and pour the sauce over them. Sprinkle with the bread and cheese mixture. Spread 40 g butter in flakes on top. In a preheated oven (electric cooker: 225 °C/ convection oven: 200 °C/ gas: see
manufacturer) Bake for 20-25 minutes until crispy brown.