Prepare chicken breasts 1 day before serving.
Cook rice according to directions on the box; set aside to cool. Flatten the chicken by lightly pounding; sprinkle with salt and pepper. Beat the egg white until soft peaks form. Add 1 1/2 cups of the cooked rice mixture to the egg white; mix well.
Cut 6 quarters from the pastry. Place each quarter on a floured board and roll larger. Place a breast in the center of each pastry and add about 1/4 cup of the rice mixture on the breast.
Roll pastry and chicken over the rice, jelly roll style. (The rolled package will look like an egg roll.) Seal ends of pastry to contain the rice. Place seam-side down in a greased baking pan. Cover and refrigerate overnight.
When ready to serve, preheat oven to 375 degrees. Remove baking pan from refrigerator and immediately place into the preheated oven. Bake uncovered for 35-45 minutes. If pastry begins to brown too fast, loosely cover with a piece of aluminum foil.
While chicken is cooking, place the jelly in a saucepan and melt. Stir in mustard, orange juice, and sherry; heat. Serve the hot sauce over the hot pastry-covered chicken. Serves 6.
