This classic variation on potatoes au gratin is a cheese-free affair. To make the recipe gluten-free, simply omit the flour and replace the milk with heavy cream, which will thicken as it cooks.
1. Preheat oven to 400°F. Coat 11- x 7-inch baking dish with cooking spray, and rub inside with cut side of halved garlic clove.
2. Place garlic halves in large saucepan with potatoes, milk, nutmeg, and salt and pepper to taste; bring to a boil. Reduce heat to medium-low, and simmer 5 minutes, or until potatoes are tender.
3. Transfer potatoes to prepared baking dish using slotted spoon (discard garlic halves). Measure flour into medium bowl, and slowly whisk remaining hot milk mixture into flour until no lumps remain. Pour sauce over potatoes. Bake 1 hour, or until top is golden brown.