1) In a large dry skillet, toast the chillies, fennel seeds, coriander seeds and peppercorns over medium-high heat until fragrant, about 2 minutes. Add to a spice grinder and run until you have a fine powder. In a large mixing bowl combine the spices with the remaining rub ingredients. Makes about 400g.
2) Rub the brisket all over with the spice rub mix. Wrap tightly in plastic and marinate overnight in the refrigerator.
3) Preheat the oven to 150 degrees C/Gas 2.
4) Line a large roasting tray with aluminium foil and set over high heat. Put the soaked chips on top, then put the pan directly over the hob to get the chips to start smoking, about 10 minutes. Place a V-rack over the top of the chips and put the marinated brisket on the rack. Cover the entire top of the roaster with foil, crimping the edges to form a nice seal, (you may have to use 2 strips foil to cover everything). Reduce heat to medium and smoke the brisket for 15 minutes.
5) Whilst the brisket is smoking, prepare the anchos, onion, garlic and tomatoes. Remove brisket from the roasting pan with the rack. Remove the chips with the foil and discard in sink (pour water on top of chips to stop smoking).
6) Put the reserved chillies and vegetables on the bottom of the pan, then put the rack with the smoked brisket in the roasting pan so it sits above the aromatics. Put in the middle of the oven and roast until brisket is tender, about 4 to 4 1/2 hours
7) Remove brisket from oven and set aside to rest. Add the pan drippings and the vegetables from the bottom of the pan to a blender and puree. Stir in the red wine vinegar and transfer the sauce to a serving dish. Slice the brisket across the grain, arrange on a serving platter and serve with sauce.