How to Make It
Preheat the oven to 450°. Cut four 12-inch sheets of heavy-duty aluminum foil. Season the fish with salt and pepper. Place 1/2 teaspoon of butter in the center of each foil sheet. Lay a fillet on each sheet and top with 1/2 teaspoon of butter and one 4-inch sprig of rosemary. Enclose the fish in foil, crimping the edges to form a tight seal. Bake for 1- minutes, or until the fish is opaque throughout. Transfer the fish to plates and garnish with rosemary sprigs.