2) Meanwhile, in a medium bowl, toss the potatoes with the rosemary, oil and salt. Preheat the oven to 200C/Gas 6.
3) For the sweet and sour sauce, in a small saucepan bring the sugar, vinegar and orange juice to a boil. Reduce the heat to a simmer and continue cooking the sauce until it reduces by half, about 10 minutes. Remove from the heat, swirl in the butter and keep warm before using.
4) When the pork has marinated, heat the 2 tbsp of oil in a 33cm cast iron oven-proof pan. When the pan is smoking hot, add the pork and sear on both sides. Add the potatoes and place in the oven until the pork is cooked through and the potatoes are tender, about 40 minutes.
5) Serve the pork steaks with rosemary potatoes and drizzled with the sweet and sour sauce.