Wash the schnitzel and pat dry. Season with salt and pepper and turn in flour. Cut the leek into rings, cut the onion and tomatoes into small cubes.
Heat the oil and fry the leeks with the onions. Stir in tomatoes and simmer for 5 minutes. Add the cream and creme fraiche and bring to the boil briefly. Add the Gorgonzola and let it dissolve. Season to taste with salt and pepper.
Place the schnitzel in a baking dish and pour the sauce over them. At 150 degrees in the oven for about 1 1/2 hours. Delicious baguettes or rice go well with this.