Chop finely and boiled in wine with bay leaves and parsley (the amount is optional) until the liquid remains half. Gently fry flour with the butter and finished with diluted liquid. Add salt and pepper and boil the mixture for 10 minutes on low heat. Clean and chopped mushrooms sauté in a little butter and add to the sauce, which is boiled for several minutes with them. Remove from heat and serve warm to veal.