Duck Fat & Goose Fat

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You can substitute duck fat for goose fat and vice-versa. They both have a high smoke point so can be heated to quite high temperatures, so are ideal for roasting potatoes to golden crispness, and both have a better flavour for roast potatoes than oil. Generally goose and duck fat are bought in either cans or vacuum sealed jars and once the cans or jars are opened the fat should be stored in the refrigerator. Duck and goose fat keeps very well in the fridge and the label on the packaging should give guidelines as to how long the fat will keep after opening, but in most cases it should keep for at least 3 months. It will start to smell and taste rancid once it is too old so do use your nose as a guide. It also freezes well so if you are buying in large quantities you can divide it up and freeze in manageable portions.

It does appear that you can re-use duck and goose fat but you must be very careful to remove any impurities in the fat as they will burn next time you heat the fat up. Let the fat cool down then strain it through a sieve lined with muslin before refrigerating. You will find that roast potatoes absorb a fair amount of fat so it is unlikely that you will have much left over in the roasting pan but if you do want to "stretch" the use of your duck or goose fat then you could always try roasting your potatoes with half duck or goose fat and half oil (a flavourless type such as sunflower, vegetable, corn, canola or groundnut/peanut).