Step 1

Peel the potatoes, leaving the smaller ones whole and cutting the larger ones so that they are all roughly the same size. Put them in a large pan of cold salted water, bring to the boil and simmer gently for about 15 mins until cooked through. Tip gently into a colander and leave to drain and cool – there’s no need to shake. When they stop steaming, put them on a tray in a single layer and place in the fridge, uncovered, until ready to roast. Can be done up to two days ahead.

Step 2

Spoon the goose fat into a flameproof roasting tin and heat on the hob for a few mins. Turn the heat off and, one at a time, turn each potato in the fat so they are completely coated. Make sure they are in a single layer and not touching. Once the oven has heated to 180C/160C fan/gas 4, put the potatoes in the oven and cook for 40 mins undisturbed.

Step 3

Remove from the oven and, again, turn each potato. Return to the oven for 20 mins, then remove and repeat the turning process. Turn the oven up to 220C/200C fan/gas 7 and cook the potatoes for a final 20 mins. Add the rosemary and garlic 5 mins before the end. Once cooked, the potatoes should be deep golden and crunchy on the outside and fluffy in the middle. Sprinkle with sea salt and serve.