1. Preheat oven to 325F. Place brisket in a roasting pan. Sprinkle with soup mix and tomatoes, then top with tomato sauce. Pour wine over everything. Cover with 18-inch-wide heavy-duty foil. A tight seal is necessary to retain juices.
2. Bake in center of oven 2 hours, then carefully open foil and add mushrooms. Recover to seal tightly, and bake 2 hours more, until fork-tender.
3. Remove meat and place in a shallow storage container. Strain gravy into a separate container, reserving vegetables. Refrigerate meat, gravy and vegetables for several hours or overnight.
4. Skim and discard any congealed fat from cold gravy. In a saucepan, bring gravy to a boil. Add reserved vegetables and season with salt and pepper. Simmer about 5 minutes to thicken and reduce slightly. Trim obvious fat from top of meat and discard. Cut meat across the grain into 3?8-inch slices. Arrange in ovenproof pan and top with gravy. Cover with foil. Reheat in a 350F oven 30 minutes or until warmed through. Serve with any of our sides or simple roasted potatoes.