In a small bowl make a rub using 2tbsp olive oil, 2tsp dried mixed herbs and 1tsp of black pepper. Smear 800g of beef brisket with the rub. Heat some butter in an ovenproof casserole pan/pot and sear the brisket all over.
Remove the brisket and fry one chopped red onion in the pan for 5mins along with 1tsp QC. In a jug of 300ml of water mix 3tbsp tomato purée and 1tbsp of garlic purée and add to the onion. Place the brisket back into the pan and add 500ml of tomato passata, bring to a simmer then lid on and place in the oven at 160fan for 3.5hrs. Add chunks of chorizo then back in the oven for at least another hour or as long as you can. Pull apart and serve on bread rolls.