Heat the oven to 400 degrees. Spray a 15 x 10-inch jelly- roll baking pan with cooking spray; set aside. In a 9-inch pie plate stir together flour, ½ teaspoon paprika, ½ teaspoon salt, and ¼ teaspoon pepper. Take one chicken breast and coat with the flour mixture. Dip both sides of the coated chicken breast into the egg whites. Then press the crushed pecans into each side of the chicken breast. Set the coated chicken on waxed paper for 10 minutes to dry. Repeat with remaining chicken pieces. Place the pecan coated chicken breasts on a pan sprayed with baking spray. Bake for 4 minutes; carefully turn the chicken breasts over and continue baking for 4 to 5 minutes or until chicken registers 160 degrees in the center of the chicken breast with a meat thermometer. Remove the chicken from the oven and keep warm. Meanwhile, in small mixing bowl, stir together sour cream, mustard, ¼ teaspoon paprika, and salt and pepper to taste. To serve, place each chicken breast on a serving plate and top with a dollop of the sour cream mustard sauce. Refrigerate leftovers.