From the Simply Recipes site:
1 Place peeled, cut potatoes into a 2 quart-sized pot. Cover with an inch of cold water. Add a tablespoon of salt to the water. Cover and bring to a boil. (Keep your eye on the potatoes, it's easy to overcook them.) As soon as the water is boiling, uncover and boil for 6 minutes, or until the potatoes are just tender enough so that you can insert a fork into them. The potatoes should be on the slightly underdone side.
2 Drain the potatoes and put them immediately into a serving bowl. Layer the cheese slices over them and put a plate over the bowl to cover, so that the steam from the potatoes melts the cheese. Let sit for several minutes, then gently fold over with a spoon to spread the melted cheese around. Pour cream over and cover again until served.
If the potatoes are on the over-cooked side and fall apart as you toss them in the cheese, you can add the cream anyway and mash them for spicy, cheesy mashed potatoes. If the potatoes are still not quite cooked enough and the cheese is not quite melted enough, you can put them in a microwave for 20 seconds or so.