Cut the pork lengthwise, and lightly slash the meat with a sharp knife. Tie up the two pieces of meat with string to hold their shape while cooking. Crush the leek, garlic and ginger together. A food processor works very well for this. Combine the condiments with the remaining ingredients and mix well. Pour over the pork and marinate in the refrigerator for three hours, using a non-aluminium shallow pan. Turn over the pork occasionally.

Preheat the oven 400F (200C). Grill the pork for about 40 minutes, brushing with the remaining marinade at least twice during the cooking process. Cool slightly, remove the string and slice thinly.