Scale the fish. Wash them and pat them dry with paper towels. Slit along the backbone, then continue cutting horizontally to detach flesh from the bone. Repeat on the other side, then snip the backbone at each end and discard it. Clean the stomach cavity of the fish and reshape it. Deeply slash each side so they cook evenly.
Mix 2tablespoons of the verjuice with the ginger, cinnamon, pepper, nutmeg, cloves, cardamom and salt. When it is a smooth paste, stir in the remaining verjuice. Brush the fish with the mixture, set them on a barbecue rack and broil/grill, basting with the verjuice mixture, for 5-10 minutes, depending on the thickness of the fish. Turn over, baste again, and continue cooking until the fish flakes easily when tested with a fork.