For the sauce:
For the tangy lime dip:
Place all the sauce ingredients in a large bowl and whisk lightly to mix well.
Season the beef.
Heat the oil in a large frying pan and, over a high heat, brown the meat well on all surfaces.
Transfer the meat into the slow cooker or in a deep casserole dish and pour the sauce ingredients over the meat.
Cook on low setting of slow cooker for 6-8 hours, or 4 hours in oven 150˚C / 130˚C fan / Gas 2, until the meat is very tender and shreds easily.
Remove the meat from the sauce and, using forks, shred the meat. Add some or all of the sauce to the shredded meat and use to fill the tacos or lettuce cups. Top with the tangy lime dip, pickled red cabbage, chopped coriander.