Partially freeze lamb. Thinly slice into bite-size strips.
In a 2-cup measure stir together 1/3 cup water, oyster sauce, cornstarch, grated gingerroot, and chicken bouillon granules.
Micro-cook, uncovered, on 1% of power for 1 1/2 to 2 minutes or till thickened and bubbly, stirring every 3 seconds.
Set aside. In a small nonmetal bowl combine bok choy, sliced mushrooms, and 2 T water.
Cover with vented clear plastic wrap.
Micro-cook, covered, on 1% power 3 to 4 minutes or till bok choy is just crisp-tender.
Drain. Cover and set aside. Preheat a 6 1/2-inch microwave browning dish on 1% power for 3 minutes.
Add cooking oil to browning dish.
Swirl to coat dish. Add lamb strips. Micro-cook, covered, on 1% power for 1 1/2 to 2 1/2 minutes or till lamb is done.
Drain off fat.
Stir in oyster sauce mixture with toasted pine nuts and bok choy mixture.
Serve over hot cooked rice if desired.