1 clove garlic, peeled
Rub the gratin dish with the cut garlic. Smear the inside of the dish with 1 tablespoon of butter.
Use a madoline to slice the potatoes to 1/8-inch thick rounds. Place one layer of potatoes side by side, slightly overlapping, on the bottom of the dish. Season with salt, pepper, thyme and a grate or two of fresh nutmeg. Top with 1/3 of the cheese and drizzle 1/4 cup of cream. Arrange a second layer of potatoes, repeat with the seasonings, 1/3 of the cheese and 1/4 cup of cream. Press the potatoes down with your fingers as you go, letting the cream soak up through the layers.
Arange another layer of potatoes on top, season with salt, pepper, thyme, nutmeg and finish with a layer of cheese. Drizzle 1/4 cup of cream. The cream should cover the potatoes but not too "liquidy". If it seems dry, add a little more cream.
Bake for 45 minutes until the potatoes are tender, the cream has been absorbed and the top is nice and golden brown.