Melt the lard in a frying pan and brown the veal. Transfer the browned pieces to an ovenproof casserole or Dutch oven. Pour out the lard in the frying pan and add the Cognac. Cook over low heat, scraping the bottom of the pan with a wooden spoon to dislodge any attached meat particles. Pour the cognac into the Dutch oven. Add the shallots, bouquet garni, wine, salt and pepper. Bring to a boil. Reduce heat, cover and simmer for 1 hour, stirring occasionally. Remove the meat from the casserole and keep warm. In a small bowl whisk together the butter and flour until a paste is obtained. Add the flour-butter paste to the sauce a little at a time, whisking constantly. Bring to a boil. Add the mushrooms and meat to the Dutch oven. Cook 15 minutes more. Serve with boiled new potatoes.
