1) Saute the mushrooms in 1/2 tablespoon of butter for 5 minutes. Add the garlic and onion and continue to saute until the onion is transparent.
2) Stir in the tomatoes, salt, tarragon, and wine. Lower heat, cover, and simmer for 30 minutes. Stir a few times while cooking.
3) Lightly season the veal with salt and pepper. Place veal in another pan with remaining butter and saute until lightly browned. Pour sauce from other pan over veal, cover, and simmer for 5 minutes. Remove and sprinkle with Parmesan cheese and serve.