Combine the raclette and Gruyere in a bowl and add the cornstarch. Toss well to coat the cheeses in the cornstarch; set aside.
In a pot over medium heat, warm the wine, garlic and lemon zest. Do not allow this to come to a boil or the fondue may be grainy in the end.
Slowly add the cheese mix a handful at a time, stirring and allowing each handful to melt completely before adding the next. Repeat until all the cheese is in the pot. Once completely smooth, stir in the kirsch, pepper and mustard. Pour the mixture into a fondue pot with a burner underneath to keep warm. Serve with Crusty Bread, apples and pears.
Preheat the oven to 350 degrees F.
Put the loaf of bread on a baking sheet and bake for 15 minutes to crisp. Allow to cool, then tear into chunks for serving. Set aside.