Combine egg white, cornstarch, sherry, 1/4 teaspoon salt and pepper in a small bowl. Whisk until smooth.
Combine sliced chicken and egg white mixture, and mix well. Set aside.
String snow peas. In a large bowl, combine snow peas, mushrooms, celery, water chestnuts and carrot.
In a wok or large Dutch oven, heat 2 tablespoon oil and add 1 teaspoon salt. Sauté vegetables for 2 minutes. Remove from pan.
Heat 2 tablespoons oil in same pan. Stir fry garlic for 30 seconds and then add chicken meat, cook for 1 minute over high heat. Add soy sauce and sugar. Mix well.
Add cooked vegetables and sliced scallion and mix for 1 more minute. Remove to heated plate.