How to Make It
Light a grill. Rub the skinless side of the fillets with 1 tablespoon of olive oil. Sprinkle with the rosemary and season with salt and pepper. Sandwich the fillets together to re-form the fish. Rub the skin with another tablespoon of olive oil and season with salt and pepper. Loosely tie the fillets together with cotton string.
Generously oil the grill. Grill the fish over a moderately low fire until just cooked through and the skin is browned and crisp, about 10 minutes per side. Transfer the fish to a platter and remove the strings. Cut the fish into 4 pieces and serve at once.