For Cheese Fondue:

1. In a saucepan, heat the wine over medium heat. Add the garlic and lemon juice.
2. Toss the grated cheeses with cornstarch to prevent clumping.
3. Slowly add the cheese mixture to the warm wine, stirring constantly.
4. Continue stirring until the cheese is fully melted and smooth.
5. Add the kirsch (if using) and black pepper.
6. Transfer to a fondue pot and keep warm over a low flame.
7. Serve with bread cubes, roasted vegetables, or fruit for dipping.

For Cheese Sauce:

1. Melt butter in a saucepan over medium heat. Stir in flour and cook for 1 minute.
2. Gradually whisk in the milk, stirring constantly to prevent lumps.
3. Once the mixture thickens, add shredded cheese, mustard powder, and paprika.
4. Stir until the cheese is melted and the sauce is smooth.
5. Season with salt and pepper to taste.
6. Serve immediately over pasta, nachos, or vegetables.