The secret to super crispy roasties.
Cut potatoes smallish and simmer them in salted water for 10 minutes, until just soft on the outside. (Yes, root veg traditionally start in cold water. I cheat here.) Drain, put the lid on and give them a good shake to rough up the edges, because those craggy bits are what go crunchy.
Let them steam dry. A tea towel over the top helps. You can do all this ahead, even the day before at Christmas. Then roast them in hot duck or goose fat. That’s what makes them super crispy.