If your slow cooker has a sear or sauté function, turn it to high. Alternatively, heat a frying pan over a high heat. For the spice paste, char the onion and tomato pieces for 6-8 mins until blackened slightly and starting to soften, turning every few minutes. This will impart a smoky flavour. Put these and the remaining paste ingredients in a food processor and blitz until smooth.

Heat the oil in the same hot pan or slow cooker and fry the brisket for 5-7 mins until golden brown on all sides. Tip in the spice paste and stir, frying for 2-3 mins until fragrant. Transfer to the slow cooker if you’ve used a pan. Pour over enough beef stock to cover the meat, then add the bay leaves and cover with the lid. Cook on low for 6-8 hrs until the meat is tender and shreds easily using two forks. Simmer, uncovered, for an extra 30 mins to reduce the sauce if needed. Check for seasoning.

Shred the meat and stir it back into the thickened sauce. Serve the beef in the tortillas along with any toppings you like, with lots of lime for squeezing over.