In a small bowl, combine the chili powder, salt, and garlic granules. Rub over the pork and let sit whilst you get on with the other stuff. In the basin of the slow cooker, combine the ketchup, jalapeno jelly, cider vinegar, cocoa powder, jalapeno juice and chipotle. Chop the onion into large pieces (I do mine in 8ths), and lay in the bottom of the slow cooker. Once the pork has had 5-10 minutes to mingle with the rub, put the pork into the slow cooker on top of the onions. Spoon some of the juicy mixture onto the top of the pork. Cover and cook on low for 6 hours.

When fully cooked, take the pork out of the slow cooker and remove the layer of fat. Strain the sauce into a bowl to remove any lumps of meat or onion and set aside. Shred the pork with two forks. Spoon over the leftover sauce until the meat is coated but not sloppy (unless you like a lot of sauce, then knock yourself out). 

Serve with warmed corn tortillas, condiments, and beer. 

Makes enough for 4-6 people to have 2 tacos each depending on piggishness.