Brussels Sprout and Chicken Stir-Fry

In a bowl whisk together the egg white and 1 tablespoon of the cornstarch, add the chicken, and let the mixture stand for 10 minutes. In a large saucepan of boiling salted water cook the Brussels sprouts for 2 1/2 minutes, or until they are just crisp-tender, drain them in a colander, and refresh them under cold water. Heat a wok over moderately high heat and in it heat the peanut oil until it is hot but not smoking. Add the chicken, drained, stir-fry it for 45 seconds to 1 minute, or until it is opaque and just firm, and transfer it with a slotted spoon to a bowl. Heat the oil remaining in the wok until it is hot but not smoking and in it stir-fry the shallot, the garlic, and the gingerroot for 30 seconds. Add the bell pepper and stir-fry the mixture for 2 minutes. Add the scallions and the Brussels sprouts and stir-fry the mixture for 1 minute. In a small bowl whisk together the soy sauce, the sugar, the vinegar, the broth, the sesame oil, the remaining 1 teaspoon cornstarch, and the cold water, make a well in the center of the vegetables, and whisk the soy sauce mixture into the well. Bring the liquid to a boil, stir together the vegetable mixture to combine it well,and simmer it for 1 minute. Stir in the chicken and the water chestnuts, season the stir-fry with salt and pepper, and cook it for 30 seconds, or until the chicken is heated through.