These are meant to accompany a roast duck main. Not everyone has duck fat in the pantry, so substitute butter if necessary. It won't have the same taste or crispness, though, so first try asking for duck fat at specialist food shops. Once you have tried these potatoes, you'll never want to cook them any other way.
- Using a 4cm cookie cutter, make deep cutouts from the centre of each potato, then cut each cylinder into 3cm-thick discs.
- Mash the remaining potato and set aside for another day. Melt the duck fat in a heavy frying pan, then add the garlic.
- Sprinkle with the thyme, then season with salt and pepper.
- Slide the pan into the oven with the duck and cook for 20-30 minutes until golden.