Rosemary roasted potatoes

Method

1. Cut the potatoes in half or quarters, depending on their size. Parboil in a large pan of boiling, salted water for 7 minutes. Drain and return to the pan to dry out. Shake the potatoes to rough up the edges. Lay out on a baking tray and cool. Once cold, put the tray in the freezer for 2 hours, then transfer to freezer bags and freeze for up to 1 month.
2. To cook, preheat the oven to 200°C/fan180°C/gas 6. Heat the oil or fat in a large roasting tin for 5 minutes until very hot. Tip in the frozen potatoes and the rosemary leaves, turning well to coat. Roast for 1 hour 10 minutes, turning halfway. Sprinkle with extra rosemary sprigs and sea salt to serve.