Soak cashews overnight or for at least 6 hours. Or cook them, it's up to you. They do turn out better soaked, though.
Peel and clean potatoes. Cut them in 2mm thick slices. Keep them in water until you have to use them.
Strain cashews. Add milk and spices and blend them well, using a high-speed smoothie-maker or hand blender. Pour that mixture into a pan and cook it for a few minutes so the sauce thickens a bit.
Grease your baking tray with coconut oil or olive oil. Place sliced potatoes on the bottom of the tray, creating the first layer. Place slices one next to another so there's only one layer of slices. Season it with a little bit of salt. Pour a bit of sauce over this layer. Create a second layer and a third one. Don't forget the salt and the sauce! This should be it, but if you have a few more potatoes, then place them around the top layer. On the very top, there should be a layer of sauce. Bake this whole thing in a preheated oven at 180°C for 1hour and a half. First, bake au gratin potatoes without aluminum foil. They should be starting turning brown now. For the last 30 minutes, cover the tray with aluminum foil so potatoes have enough humidity to soften up well.
Serve as a main dish, or as a side dish next to a sauce, tofu, tempeh, salad, grilled veggies, etc. Bon appetit!
