1. Preheat a gas or charcoal grill.
2. Heat 3/4 cup water, 1 cup orange juice and soy sauce in a small saucepan until just simmering. Pour into a medium bowl; stir in rice and scallion whites and set aside, uncovered, for 10 minutes. Whisk hoisin sauce, ginger, sesame oil and the remaining 2 tablespoons each of water and orange juice in a small bowl.
3. Stack two 20-inch sheets of foil (the double layers will help protect the ingredients on the bottom from burning). Coat the center of the top layer with cooking spray. Place one-fourth of the rice mixture in the center. Set a piece of fish on the rice. Arrange 3 wedges of plum on the fish. Top with one-fourth of the hoisin mixture and sprinkle with one-fourth of the scallion greens. Bring the short ends of the foil together, leaving enough room in the packet for steam to gather and cook the food. Fold the foil over and pinch to seal. Pinch seams together along the sides. Make sure all the seams are tightly sealed to keep steam from escaping. Make 3 more packets with the remaining ingredients.
4. Place the packets on a gas grill over medium heat or on a charcoal grill 4 to 6 inches from medium coals. Cover the grill and cook until the fish is opaque in the center, 8 to 12 minutes, depending on the thickness. (When opening a packet to check for doneness, be careful of steam.) Use a spatula to slide the contents of the packet onto a plate.

Yield: 4 servings