1. To make the marinade, in a small bowl, stir together the garlic, shallots, lemon juice, and lemon zest. Add the olive oil and stir until blended. Season with salt and pepper.

2. Arrange the swordfish steaks in a large, shallow non aluminum dish. Pour the marinade over the fish, coating evenly. Cover and refrigerate for 2 to 4 hours.

3. Prepare the barbecue for medium heat grilling.

4. To make the sauce, in a medium bowl, whisk together the parsley, shallot, garlic, lemon zest, capers, gherkins, lemon juice, and salt and pepper to taste until combined. Pour in the oil in a steady stream, whisking until well incorporated. (You can also do this in a food processor using a pulsing action. Be careful not to puree the mixture.) Taste for seasoning.

5. Remove the fish from marinade. Grill the fish about 3 inches from the fire, turning once, for 5 to 6 minutes on each side for medium rare, or to desired doneness.

6. Transfer the swordfish to a serving platter and spoon the herbed green sauce on top. Serve immediately