Rub the beef joint with oil, season well with half tsp salt and pepper then coat in the corn flour. Heat a pan to a high heat and place in the meat to sear each side until starting to turn golden, this will take approximately 1 minute per side. Remove from the heat and set aside.
In a bowl mix the paprika, smoked paprika, coriander, cumin, ground chilli, chipotle flakes, brown sugar and remaining salt to make the Mexican rub. Smear this evenly all over the meat ensuring that it is coated well.
Place the sliced onion, crushed garlic and finely chopped fresh chilli pepper into the slow cooker. Then melt the beef stock in the hot water and pour this in the cooker. Add the tomato paste, tomato passata, molasses and cider vinegar and stir through well.
Place the beef into the slow cooker carefully, ensuring that the rub stays on the meat and is not washed off by the stock. Cook on low for 8 hours (or high for 4)
Once cooked, remove the meat from the cooking pot and cover with foil. Use the stock in the pot as a sauce for the meat, it should already have thickened due to the corn flour on the meat but to create a richer, stickier glaze place the sauce in a pan on the stove over a high heat for 15-20 minutes to thicken further.
While the sauce is thickening, take two forks and shred the beef. When the sauce is thickened pour this over the meat coating well and then serve with fresh tacos, salsas and sour cream.
Notes
Gluten freeThis recipe does not contain gluten.NoteHalf a red chilli pepper was used in this recipe to add heat to the sauce however, adjust the quantity of fresh and ground chilli according to taste and the strength of the fresh chilli being used.