Put the mojo marinade ingredients into a blender with some seasoning and blend until smooth. Put the pork into a large food bag, pour in ¾ of the marinade and rub and toss well. Leave to marinate in the fridge for 12-24 hours – the longer the better. Pour the left-over marinade into a bowl, cover and chill.
Heat the oven to 220C/fan 200C/gas 7. Put the pork and marinade into a roasting tin, cover tightly with a double layer of foil and roast for 30 minutes. Turn the oven down to 160C/fan 140C/gas 3 and cook for another 2 hours, basting regularly, until really tender and juicy. Remove to a plate and cover with foil until completely cool, then wrap tightly in clingfilm and chill for at least a few hours. Meanwhile skim off the fat from the sauce in the roasting tray, pour the remaining sauce into a bowl, cover and chill. Once chilled, slice the pork into 1cm slices and heat the oven to 180C/fan 160C/gas 4. Pour the reserved sauce into a roasting tray, along with the leftover fresh marinade, add the pork slices, cover with foil and heat for 15 minutes until hot.
Heat a large frying pan and brush the cut sides of the sub rolls liberally with mustard. Layer up the sandwiches with the pork, ham, cheese, pickle slices and more mojo sauce. Brush the outside of the sandwiches with melted butter, then put into the pan, in batches if necessary, and put a heavy frying pan on top to weigh them down. Fry until golden and crisp, pushing down gently on the pan. Flip and repeat on the other side then serve with more pickles. You can make more sandwiches with any left-over pork. Enjoy!