Preparation: Cut lamb across grain in slivers about 5 cm long. In bowl, sprinkle lamb with salt & cornstarch; rub into meat; add sherry. Marinate lamb for 15 minutes. Trim & cut scallions in 5 cm pieces. Halve, core & slice bell pepper into slivers to match lamb. Combine stock, soy sauce, sugar and vinegar; reserve. Cooking: Heat peanut oil in wok to deep-fry temperature (bubbles form around dry chopstick held upright in oil). Fry lamb slivers briefly, until coating of starch begins to brown. Remove to strainer & reserve. Remove oil from wok and save. Wash wok. Return wok to high heat. Add 2 T oil to very hot wok. When oil starts to smoke, add scallions & bell pepper. Stir-fry for 30 seconds; add garlic & ginger. Keep stir-frying. When pepper turns bright green, add stock mixture. Stir until liquid boils and reduces slightly. Add lamb. Stir-fry until lamb is hot. Serve.