150ml sour cream
2 cloves garlic, thinly sliced
1 heaped teaspoon minced black truffles (I use these ones, from Amazon)
Salt, pepper & nutmeg
Beat together the sour cream and truffles and season with salt, pepper and nutmeg. Peel and thinly slice your spuds. Place a layer in an oven-proof casserole dish, then scatter with some slices of garlic and sprinkle on a scant spoonful of the sour cream mixture. Repeat until you run out of potato, then pour over the rest of the sour cream mixture.
Bake in a 180C oven for about an hour, covering with foil if it looks like it is getting too dark. About 15 minutes before the end, sprinkle on a thick layer of grated cheese (this was a mix of cheddar and mozzarella, but whatever you like) and return to the oven until the cheese is melted and golden brown and the potatoes are tender all the way through.