Preheat oven to 400°. Cut 4 (15- x 13-inch) sheets of parchment paper. Fold each in half lengthwise, crease, and lay flat. Place 1 fillet on half of each parchment rectangle near the crease. Sprinkle evenly with butter and remaining ingredients. Fold parchment paper, sealing the edges with narrow folds, and place packets on baking sheet(s).
Bake 13 to 15 minutes or until packets are puffed. Place on serving plates, and cut open.