Seriously satisfying… and if you harbour any guilt do not attempt this dish. One of the truly great potato dishes.  Layers of potato cooked in a rich garlic cream topped with a generous sprinkling of Gruyere cheese. This dish goes best with any roast, especially beef. The variety of the potatoes is very important, I found that Desiree or Belle de Fronteney are the best and both are usually available in supermarkets. The Gratin can be cooked an hour before the meal and reheated 20 minutes before required.