Roasted Duck Breasts with Stone Fruit Mostarda

Ingredients

• 2 pounds assorted pieces of stone fruit- nectarines, plums and apricots, about 2 pounds
• 1/4 cup light brown sugar
• Olive oil
• 1 shallot, minced
• 1 1/2 teaspoon red wine vinegar
• 1 teaspoon grainy dijon mustard
• 2 teaspoons dijon mustard
• Kosher salt
• freshly ground black pepper
• 6 duck breast halves with skin (about 1/2 pound each)