Toss the 2 cheeses together with the cornstarch. Rub the inside of a heavy saucepan with the cut garlic clove. Add wine and 2 tablespoons Kirsch and bring to a boil. Reduce the heat to medium-low and add the cheese mixture, stirring, until mixture is hot and smooth.
Add remaining 2 tablespoons Kirsch if mixture is too thick. Season with nutmeg and pepper, to taste. Transfer to a fondue pot and serve immediately with dippers of choice.