Pork-fat roast potatoes

1.Preheat oven to 250C. Cook potato in a large saucepan of boiling salted water until par-boiled (10 minutes), drain and set aside.

2.Strain pork fat into a flameproof roasting pan, add lard and cook over high heat until hot. Add potato (be careful as hot fat will spit), toss to coat, season to taste, then roast in oven, turning occasionally, until golden and cooked (30 minutes). Add rosemary to pan a few minutes before potatoes are ready. Scatter with sea salt and serve hot.