Put the milk, cream and cream cheese in a saucepan. Place the rosemary sprigs in the saucepan and squeeze the garlic. Season well with salt, pepper and nutmeg. Heat while stirring until the cream cheese has dissolved.
Cut the potatoes into thin slices and simmer in the sauce for 5 minutes. Take out the rosemary. Put everything in a baking dish and sprinkle with cheese. Place in the oven preheated to 200 degrees for about 35 minutes.