In a large deep dish, heat the oil. Add the diced onion and fry for 5 minutes. Then stir in the cumin, coriander and garlic slices, chipotle paste and dark brown sugar. Season with salt and pepper, and cook out the spices.
Remove from the heat and place in a blender and pulse it until smooth.
Rub this marinade over the beef brisket in the large deep dish. Marinade for at least 3 hours.
Heat the oven to 120Â°C fan / 140Â°C.
Pour the beef stock, orange juice, passata and red wine in a large jug.
Pour the mixture into the dish with the marinaded beef brisket. Cover with a lid and slow cook for 5 hours. Turn the meat halfway through.
Once the brisket is cooked. Place the brisket in a roasting tin. Move the pan to the hob and reduce down to a thick BBQ sauce.
Finish the brisket by pouring over the BBQ sauce and grilling for 5 minutes. You will have excess sauce so you don't need to pour all of it over. Serve with fresh baked bread or wraps with avocado, green salad and remaining BBQ sauce.