Have all ingredients ready to use. Dredge the veal in flour so that it is thoroughly covered. In a very large frying pan melt the butter over low heat. Add, the onion, shallots, and garlic, raise the heat to medium, and cook for about 2 minutes. Add the mushrooms and stir. Add the medallions of veal, and cook about 2 minutes on each side. Add the tablespoon of flour reserved for thickening the sauce. Stir to distribute. Add beef stock, white wine, tarragon, chervil, basil, parsley, salt, and pepper. Simmer for a few minutes. Add the tomatoes and continue cooking just long enough to heat the tomatoes. Serve immediately in warmed dishes.