Peel and halve the potatoes, ensuring all pieces are a similar size.
Place potatoes in a saucepan with rosemary, garlic, bay, and peppercorns.
Cover with cold water, bring to a boil, and simmer for 5 to 7 minutes.
Drain the potatoes and allow them to steam dry in a colander for 10 minutes.
Preheat the oven to 220°C.
Heat the goose fat in a roasting tin in the oven for 5 minutes until very hot.
Carefully add the potatoes and aromatics to the hot fat and roast for 20 minutes.
Remove the tin and gently squash the potatoes to increase surface area.
Roast for another 20 minutes until the potatoes are golden-brown and crisp.
Discard the aromatics, season with salt, and serve.