Set the oven to Gas 8, 230°C, fan 210°C.
Peel most of a 2.5kg bag of potatoes. Use medium-large potatoes, and cut into halves and quarters to make them approximately the same size.
Stick the potatoes in a large pan and just cover them with cold water. Put the lid on and bring to the boil.
Meanwhile, get a large, shallow earthenware or glass oven dish and put it in the oven, empty, to heat up.
Once the potatoes are boiling, lower the heat and let them simmer for 10 minutes. Scoop two dessertspoons of goose fat into the oven dish. Getting the fat really hot is key.
Check the potatoes after 10 minutes - test them with the tip of a sharp knife. If the outside is soft but the inside is still hard, then they're ready. Drain the potatoes, pouring the potato 'stock' into a jug so you can use it for your gravy later. When all the water is drained off, jiggle the pan around to rough up the surface of the potatoes.
Get the oven dish out, the goose fat should be melted, clear and visibly hot. Carefully tip the potatoes from the pan into the oven dish. If you’ve got it right, they’ll sizzle on impact. Use a serving spoon to turn them in the fat so they get coated all over.
Put the dish in the oven and turn the potatoes after about 20 minutes. Check again after 40 - 50 minutes to make sure they're not getting too dark.
If the potatoes are getting ahead of the rest of the roast dinner, put them down to a lower shelf, cover them with foil or lower the oven temperature. You want to keep them hot, but without over-browning them.
If you serve on most Sundays to the family, over time you'll get the hang of it and perfect them. They will become a family favourite and Sunday roast will be a bit of a routine family event, which is nice.
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