For the Creamy Potato Gratin, how long can I leave it after cooking potatoes in the pan before transferring to the dish to bake in oven? Am I okay to leave them for about an hour?
Nigella's Creamy Potato Gratin (from NIGELLA BITES) is slightly different to traditional gratins as the potatoes are cooked in a saucepan first and then transferred to a hot oven to finish. It is possible to cook the potatoes in advance and they can sit for up to 2 hours before being transferred to the oven. It may be easier to transfer them to the baking dish and let them sit in the dish until ready to bake, as the mixture will thicken as it stands. You may also need to allow an extra 10 minutes in the oven, or until the potatoes are piping hot in the centre, as the potatoes will have cooled down while they stand.
The potatoes can be simmered and the gratin can be assembled up to 2 days in advance, covered and stored in the fridge until ready to bake. Refrigerate the gratin as soon as it is cool enough, and within 2 hours of cooking the potatoes. As the gratin will be cold, we suggest taking it out of the fridge 40 minutes before cooking it. It will then need to go into an oven heated to 220°C/200°C fan/450°F for about 40 minutes, or until piping hot all of the way through.