Although this popular crab dish It's often called 'roasted' or 'baked', it is not. In restaurants, the cracked crab pieces are briefly deep-fried, then quickly stir-fried and finished in a hot wok. For the home cook, I have omitted the deep-frying step. Set up finger bowls and containers for discarded shells. Serve with hot rice and soup or salad. Hold crab under cold running water and scrub with a vegetable brush, paying special attention to the underside of the body and between the legs. To kill the crab, plunge it into a large stockpot of boiling water for 1 minute, or place the crab upside down in a large bowl and cover it with boiling water. When the air bubbles stop rising to the surface, drain the crab and let cool until you can handle it. If using cooked crab, omit this ,step and proceed to cleaning. To clean cooked crab: Place crab on its back. With a knife tip lift the apron or breastplate, the triangular-shaped flap on its underside. Grab it and the spine; pull backward, twist and remove. Grab the shell portion in one hand while gathering up all the legs and claws in the other hand. Rock the legs back and forth, tearing them away, from the shell. Pull off the feathery gills from both sides of the chest, remove the mouth and mandibles from its face and discard. Rinse crab with cold water. Blot dry. You may reserve the tomalley, the green spongy matter in the body, for another use, although state and federal authorities have advised against eating the tomalley in this season's crab. To crack crab: Bend and twist legs backward to remove. With a hammer or nutcracker, crack the shell in the middle of each joint and claws, and in the middle section on the edge side of each leg. Pat dry. Using a cleaver or chef's knife, chop the body through the midsection, dividing it into 2 halves, then each half crosswise into thirds. To "roast" crab: Preheat a wok over medium-high heat. Add oil, salt, ginger and garlic and half the green onions; saute gently to release the flavors. Using the backside of a spatula, crush the ingredients against the side of the wok to squeeze out juices about 30 seconds, or until fragrant. Increase heat to high. Add crab claws and legs; stir-fry for 1 minute, or until shells turn bright orange, then toss in chest pieces and cook together for another 2 minutes. Season with the sugar and white pepper. While the wok is hot, splash the vermouth against sides, then the soy sauce. There should be a sizzle and hiss. Toss together for 10 seconds. Add chicken stock; toss to mix. Scatter remaining green onions over crab. Cover wok and "roast" or braise over high heat for 3 to 5 minutes, or until crab turns bright orange. (If using cooked crab, braise for 1 minute, or until heated through). Shake wok occasionally to redistribute crab. Remove cover. Add cornstarch mixture in center of wok and stir until thickened (about 10 seconds). When the sauce glazes the crab, fold in sesame oil. Remove to a platter. If you prefer, discard ginger and garlic. Serve immediately with steamed rice. PER SERVING (6 servings): 115 calories, 7 g protein, 4 g carbohydrate, 8 g fat (1 g saturated), 24 mg cholesterol, 641 mg sodium, 0 g fiber. Joyce Jue writing in the San Francisco Chronicle, 3/4/92.