Preheat oven to 180°C. Grease a 1.5L baking dish. Combine milk, cream and garlic in a bowl, then season with salt.
Place a single layer of potato in the dish, then pour over a little milk mixture. Continue layers, finishing with a layer of potato. Dot the top with butter.
Cover dish with baking paper, then foil. Bake for 1 hour. Uncover and bake for a further 25-30 minutes until golden and tender. Stand for 10 minutes, then serve.