Mix together the spices in a bowl, then rub over the pork. Heat 1 tablespoon of the oil in an ovenproof frying pan, add the pork and cook until browned on all sides. Transfer to a preheated oven, 180°C (350°F), Gas Mark 4, and cook for 20–25 minutes or until cooked through. Leave to rest for 2 minutes.
Meanwhile, cook the sweet potatoes in a saucepan of boiling water for 12–15 minutes until tender, adding the cabbage and leeks 3–4 minutes before the end of the cooking time. Drain well.
Heat the remaining oil in a frying pan, add the vegetables and fry for 7–8 minutes until starting to turn golden. Stir in the cream and mustard.
Slice the pork and serve on top of the vegetables.