Missy Robbins's Prosciutto With Parmesan Butter And Balsamic Mustard

Ingredients

• 1 pound butter
• 1/2 pound ground Parmigiano-Reggiano cheese
• 2 cups white wine vinegar
• 1 cup water
• 1/4 cup sugar
• 1/4 cup salt
• 1 tablespoon fennel seed
• 1 tablespoon coriander seed
• 1 tablespoon black pepper
• 1 tablespoon chili flakes
• 1 clove garlic
• 1 cup mustard seeds
• 1 cup aged balsamic vinegar
• Crusty bread and thinly sliced prosciutto