Begin by rubbing the brisket generously with the sea salt, then leave to cure for 3 hours

While the brisket is curing, prepare the salsa. Preheat an oven to 250°C/gas mark 9. Place a frying pan over a high heat and toast the guajillo chillies until they start to smoke, then transfer to a bowl and cover with the hot water. Leave to soak for 20 minutes

Meanwhile, place the tomatoes, garlic and onion on a baking tray and cook in the oven for 30 minutes or until blackened. Peel the garlic and place in a blender with the tomatoes and onion, then add the soaked chillies and the water. Blitz until chunky, then add the cumin and salt. Taste and adjust the seasoning as necessary – it should be smoky and a little spicy. Decrease the temperature of the oven to 150°C/gas mark 2

Wash the salt off the brisket and cut the beef into 8cm chunks. Place a few tablespoons of the beef or duck fat in a large ovenproof casserole dish and heat until melted. Add the beef chunks and sear on all sides until browned and crisp, then transfer to a bowl (you may need to do this in batches)

Add the rest of the fat to the saucepan and heat until melted. Add the garlic and the browned beef, stir to combine, then cover and cook in the oven for around 4 hours. The beef is ready when it is very soft and tender (you should be able to cut through it with a spoon)

Use a slotted spoon to lift the beef out of the fat and discard the garlic. Chop the meat up roughly and place in a frying pan over a medium heat. Cook for 3–4 minutes to crisp up the beef, then transfer to a bowl and keep warm

In the same pan, warm the tortillas until pliable and soft, covering them in a damp tea towel to keep warm

To serve, spoon some of the meat into each tortilla followed by a dollop of the salsa. Finish with some coriander, onion and a squeeze of lime juice