Bring a large pan of water to the boil and cook the potatoes for 15 minutes until tender.
Meanwhile, preheat the grill to medium. Season the chops with freshly ground black pepper and place on the grill pan. Grill for 4-5 minutes on each side, or until cooked to your liking. Cover with foil and leave to rest for 5 minutes.
Place the pistachios, parsley, mint, lemon juice, 1 tbsp olive oil and 200ml water in a blender or mini food processor, then whizz together for a few seconds to make a fairly smooth sauce. Season to taste with freshly ground black pepper.
Drain the potatoes and return them to the pan. Add the rest of the oil with the chilli and coriander and crush lightly with a fork. Serve the potatoes with the grilled chops and the pistachio sauce and garnish with the extra mint sprigs.