Rub the inside of a fondue pot with the cut sides of the garlic halves: discard the garlic. Pour the wine, kirsch (if using), and lemon juice into the pot and bring to a simmer over medium-low heat. Gradually add the cheeses, a handful at a time, and stir gently until the mixture is creamy and the cheeses are completely melted. Stir in the nutmeg. Taste and adjust seasonings, adding a little salt if needed.
