Rub a shallow porcelain baking dish with a small amount of butter. Rub dish with garlic, cut in half. Preheat oven to 350.
Layer half potatoes, cover with half the cheese and half the cream. Add salt. Repeat the second layer. Dot with butter, if desired. Bake uncovered, until gratin is crisp and golden on top (50-60 minutes). Add pepper to top it desired.