* Oyster sauce is an ingredient used frequently in Oriental cooking. ~- Partially freeze lamb. Thinly slice into bite-size strips. In a 1-cup measure stir together 3 T water, oyster sauce, cornstarch, grated gingerroot and chicken bouillon granules. Micro-cook, uncovered, on 100% power for 1 1/2 minutes or till mixture is thickened and bubbly, stirring every 30 seconds. Set aside. In a small nonmetal bowl combine bok choy, sliced mushrooms, and 1 T water. Cover with vented clear plastic wrap. Micro-cook, covered, on 100% power for 1 1/2 minutes or till bok choy is just crisp-tender. Drain. Cover and set aside. Preheat a 6 1/2-inch microwave browning dish on 100% power for 3 minutes. Add cooking oil to browning dish. Swirl to coat dish. Add lamb strips. Micro-cook covered, on 100% power for 1 to 2 minutes or till lamb is done. Drain off fat. Stir in oyster sauce mixture. Micro-cook, uncovered, on 100% power about 30 seconds or till mixture is heated through. Toss lamb mixture with toasted pine nuts and bok choy mixture. Serve over hot cooked rice, if desired.