Par boil potatoes for 5 - 10 minutes with a little salt in boiling water.
Line a tray with foil and put the goosefat into the oven to melt.
When the potatoes are ready, pop them into the tray of melted goosefat and pop them in the oven at around 200 - 220C for 10 minutes. Don't turn them over at this point or they may smush up.
Take them out of the oven, turn the potatoes over to coat the goosefat over all the potatoes and put them back in the oven for a further 30 minutes.
Take them out again, give them a shake and then return them to the oven for another 10 minutes. If you like them as crispy as we do, then just keep them in for a little longer.