The secret to really crisp crackling is to cook it separately. Most restaurants serving it will have deep fried the pig skin to crisp, crunchy perfection instead of oven roasting it.
To do it at home, remove the skin from your joint and dry it overnight uncovered at the bottom of the fridge. Salt it, slice it into strips and roast in a hot oven until golden and crunchy. You can serve these long crackling strips as appetisers at a party with a pot of homemade apple sauce to dunk them in.
You’ll find pork rewards a long, slow cook which means you won’t get good crackling – but you can, if you haven’t cooked it separately, stick it under a hot grill to finish.