A great decadent side to your Christmas Roast, this Potato Gratin with Porcini Mushrooms is decadent and filling enough to stand as a main dish on its own. Creamy, with strong earthy aromas of porcini and thyme, our Potato Gratin goes very well with beef, lamb or gammon, or simply with a variety of roast or steamed vegetable sides!
Pour the milk and double cream into a large pan. Add dried porcini mushrooms, thyme, garlic, shallot, nutmeg and a tsp of salt. Bring the mixture to a gentle boil and simmer for 5 minutes. Then cover with a lid and leave to cool down for 30 minutes.
Pour the cooled mixture into a blender/ smoothie maker/liquidiser and blitz into a smooth liquid.
Peel the potatoes and using a mandolin or a food processor with a slicer sttachment, slice the potatoes into 2-3mm thick slices.
Preheat the oven to 140°C Fan. Grease an ovenproof dish with butter generously.
Layer a quarter of the potatoes to cover the bottom in an even layer. Pour a quarter of the cream mixture. Then layer another quarter of the potatoes and top with the sauce again. Carry on like this until you have no potatoes or sauce left.
Top the gratin with grated parmesan, a sprinkling of salt and pepper. Cover the dish with foil and pop into the oven for 1-1.5 hours. After an hour, uncover the dish and check if potatoes are cooked through and tender by inserting a sharp knife. Once cooked, increase the oven temperature to 180°C and place the uncovered dish back in the oven for another 10-15minutes.