Preheat oven to 400°F. Place parchment squares on work surface. Generously butter half of each parchment square; top buttered half of each with 1 fish fillet. Sprinkle fish with salt and pepper; top each fillet with 3 tarragon leaves, then 1 piece of butter. Arrange asparagus around each fish fillet; pour 1 tablespoon orange juice over each. Fold parchment over fish and asparagus, folding and crimping edges tightly to seal and enclose filling completely. Place on 2 rimmed baking sheets, spacing apart. do ahead Can be made 4 hours ahead. Chill.
Bake fish packets 17 minutes. Slide packets onto plates and serve.