1. Heat oven to 400 degrees F. Place each chicken breast between two sheets of plastic wrap and pound to an even 1/2-inch thickness. Prepare four 20-by-30-inch pieces of parchment (see instructions, above right); place chicken on one side of each paper.
2. In a bowl combine parsley, garlic, zest, salt and red-pepper flakes. Divide mixture among chicken breasts, covering the surface of each piece. Sprinkle with raisins and nuts.
3. Fold parchment over chicken breasts and pleat in 1-inch increments, folding edges over tightly to seal packet. Place packets on a baking sheet; bake until packets are puffed and chicken is cooked through, 15 min.
4. Carefully transfer packets to plates, cut the paper across the top and tear to open.