Peel and cut potatoes into chunks about 5cm / 2in square.
Place in a pan of salted water, bring to the boil, then simmer for 10 minutes.
Drain the potatoes, keeping the water for the gravy.
Place the potatoes back in the pan and shake them around to roughen the edges. (You can also use a fork to scratch the edges).
Put the goose fat into a roasting tin and heat in the oven until hot, approximately 10 mins.
Add potatoes to the tin and coat with the fat.
Cook in a moderate oven for approximately 1 hour or until golden and crisp.