Set your crock pot to high (for 4 hour cooking) or low Recommended (for 6 hours).
Slice the lamb into chunks and brown in the inner aluminium dish of the Crock-pot. Remove then add the sliced onion. Cook down till soft then add the spices and cook for a minute.
Add the onion to the lamb and the rest of the ingredients apart from the salt and cornflour to the Crock-Pot and cook until the lamb is easily pulled apart with two forks. With a slotted spoon remove all the lamb chunks to a large platter and shred the meat with two forks.
Add the salt to taste and if the mixture needs thickening, mix the cornflour with a little water and add to the mix. Cook until thick (taste if you transfer to a pan and bring to the boil, then return the lamb to the mixture.
Serve with tacos and the recommended in the post toppings. (Links included in the post).