Preheat the oven to 350°F/ 180°C.

Cut the garlic clove in half and rub the inside of an ovenproof glass baking dish with it. Discard.

Layer one-third of the thinly sliced potatoes in the pan, dab with butter and sprinkle with a little salt. Combine the feta and graviera. Spread a third of the cheese mixture over the potatoes. Repeat with remaining potatoes, butter, and another third of the cheese, reserving the last third for later.

Pour in the cream.

Bake the potatoes, covered, for 40 minutes, then uncover, sprinkle with remaining cheese, and continue baking for about 10 minutes, or until the potatoes are fork tender and the cheese melted and golden. Serve hot.