Oh dear, it was really delicious! My family and I loved it and we will be making it for many more dinner parties.

Layer up: Butter a baking dish. Start with a layer of sliced potatoes, overlapping slightly. Drizzle some of the creamy mixture over the potatoes, then sprinkle with Parmesan and Gruyere. Repeat these layers until the ingredients are used up, finishing with a layer of cheese.