3/4 cup finely shredded Gruyère, Emmental, or Comté
Heat the oven to 400°F. Using a very sharp knife or a mandoline, carefully cut the potatoes into 1/8-inch slices (no thicker).
Put the potatoes in a large heavy-based saucepan and add the cream, salt, pepper, nutmeg, and garlic. Cook the mixture over medium-high heat until the cream is boiling, stirring occasionally (very gently with a rubber spatula so you don’t break up the slices).
When the cream boils, pour the mixture into a 2-1/2- or 3-qt. baking dish. If you don’t want a tender but garlicky surprise mouthful, remove and discard the garlic cloves. Shake the dish a bit to let the slices settle and then sprinkle the surface with the cheese.