Chicken Breasts Stuffed with Peaches and Cashews

6 boneless chicken breasts
3 peaches
1/2 C finely chopped onion
1/2 C cashews
1/4 tsp fresh ginger, grated
1/4 stick of butter
1 tbs demerara or muscovado sugar
1/2 tsp ground mustard seeds

Preheat oven to 350 degrees. Blanch peaches in boiling water until skin begins to wrinkle. Remove, rinse with cold water, and peel and finely chop. Pound chicken breasts to flatten and sprinkle with salt. Chop cashews with one whirl of a food processor. Combine peaches, onion, cashews, and ginger. Place a spoonful of mixture on top of chicken breast, roll, secure with toothpick. Dot with butter. Sprinkle with sugar and mustard powder. Bake for 20 minutes. Turn. Bake 20 minutes more.