Pulled firecracker brisket

Name: Pulled firecracker brisket
Ingredients: 3 tbsp vegetable oil; 2-2½kg piece beef brisket rolled (ask the butcher to do this for you); 2 red onions chopped; 1 tbsp sweet smoked paprika; 1 tbsp English mustard powder; 2 tsp ground cinnamon; ½ tsp ground cayenne pepper or 1 tsp chilli flakes (omit if you want to reduce heat); 1½ tbsp treacle; 50ml red wine vinegar plus 2 tbsp; 75g soft light brown sugar plus 2 tbsp; 3 garlic cloves crushed; 4-6 bay leaves; 2-4 fat red chillies pierced a few times with a small sharp knife; 500ml carton passata; 2 tbsp Worcestershire sauce; soured cream to serve