- Preheat oven to 425°F. Cut garlic cloves into half.
- Rub half of a clove garlic all over insides of a 3-quart shallow glass or ceramic baking dish then discard garlic.
- Rub 1/2 tablespoon butter all over dish, cut remaining butter into small pieces and reserve.
- With adjustable blade slicer or a sharp knife, cut potatoes into 1/8-inch-thick slices.
- In a deep skillet, combine potatoes, milk and remaining garlic. Heat to boil on medium flame, stir occasionally. Reduce heat to medium-low and let simmer for 3 minutes.
- Stir in nutmeg, salt and freshly ground black pepper, discard the garlic from it.
- Carefully transfer potato mixture to prepared baking dish, spreading evenly. Top with reserved butter pieces.
- Bake the gratin for 30 minutes or until golden brown with darker brown spots and potatoes are tender.
- Let cool on wire rack for 10 minutes before serving.