So delicious and so easy! I found this recipe in the November '10 issue of Everyday Food. Thanks Martha!
2-3 Idaho potatoes
1 tablespoon of butter
salt and pepper
Preheat oven to 400*. Butter each muffin tin cup. Slice the potatoes VERY thin. Layer the sliced potatoes in the muffin cups, seasoning with salt and pepper every 3 slices or so. Pour 1 tablespoon of heavy cream over each muffin cup of potatoes. Bake for 30 minutes or until very tender (test with a sharp knife). Loosen gratins around the edges with a knife. Invert on serving platter or cookie sheet.
I baked mine for a bit longer (ok, I kinda lost track of time...) and the potatoes got a bit crispy. They were still lovely!