Rinse the meat and spread the dry onion soup mix evenly onto the brisket. Allow to sit for an hour or so.
In a large heavy-based pot heat the oil and sear the meat on all sides being careful not to burn the seasoning.
Add the stock, the can of chopped tomatoes and the chilli sauce. Let it simmer.
Add the vinegar and the wine. Simmer again. Season with black pepper and salt.
Cover with a tight-fitting lid or foil, or place in your slow-cooker. If needed add more stock or water so the meat is half covered. Cook in the oven at 160ºC until the meat is tender (approximately 5-3 hours) or 8-10 hours in a slow-cooker. The meat SHOULD NOT be pink! If it is then it will be tough... You've been warned!
Adjust the seasoning as needed. Remove the meat from the sauce. Allow to cool enough to handle. Carve and serve with the sauce on top.