Method

• Put the cut potatoes in a large pot of cold salted water. Bring to the boil, then simmer 10 minutes until a knife just goes through the edge. Do not overcook.
• Drain into a colander. Shake the colander hard for 20 seconds - the edges will roughen and look chalky. This is where the crunch comes from.
• Preheat oven to 220°C fan-forced. Put the duck fat in a heavy-based roasting tray and slide it into the oven for 10 minutes until smoking.
• Carefully tip the potatoes into the hot fat. Turn to coat. Add the bashed garlic cloves. Spread in a single layer.
• Roast 25 minutes without touching. Turn once, add the rosemary. Roast another 20 minutes until deep golden and crunchy.
• Lift out, drain on kitchen paper, toss with sea salt flakes and cracked pepper. Serve immediately.