The day before cooking, begin by lightly toasting the peppercorns, cumin seeds and mustard seeds in a hot dry pan until fragrant– about 30 seconds
Transfer to a pestle and mortar or spice grinder and grind to a powder, then stir in the rest of the spices. Apply the rub all over the ribs and leave to cure overnight in the fridge
Preheat the oven to 180ºC/gas mark 4 or set up a barbecue to cook over in-direct heat (either by using heat deflectors or setting up the coals at one side so you have a hotter and a cooler cooking side of the barbecue)
Cook the ribs either in the oven or over in-direct heat on the barbecue for 90 minutes, basting with cider vinegar every 20 minutes to prevent them from drying out
Slice in between each rib and serve up hot