Can I pre-prepare the Creamy Potato Gratin the day before, store it in the fridge and do the final bake on the day? Will it store well in the fridge?
Nigella's Creamy Potato Gratin (from NIGELLA BITES) is slightly different to a classic gratin as the potatoes are simmered on the stove with onions, garlic and cream, before being transferred to a dish and baked. It is possible to pre-prepare the gratin up to 2 days ahead by simmering the potatoes and transferring them to the buttered baking dish, then refrigerating them until needed. You should cool and refrigerate the mixture as quickly as possible, and within 2 hours of cooking.
Very occasionally some of the edges of potatoes that are exposed to the air can oxidise and turn grey (it is still fine to eat). To reduce the risk of this happening press a piece of baking parchment (parchment paper) or clingfilm (plastic wrap) onto the surface of the gratin and then cover tightly with clingfilm. However this discolouration does not usually show once the gratin has been baked. You will need to bake the gratin in a slightly different way as it needs to be reheated first. If possible, remove the gratin from the fridge about an hour before baking it, to let it lose its fridge chill. Preheat the oven to 180c/350F, unwrap the gratin and dot the top with the remaining butter. Bake the gratin for about 50 minutes, until it is bubbly and piping hot all of the way though. If the top is not golden then increase the oven temperature to 240c/450F and bake for another 5-15 minutes, keeping an eye on the dish to make sure that it doesn't burn in the hot oven.