Preparation: Trim ends off green onions and cut light green and white part into 3 cm sections. Mix all other sauce ingredients in 2 litre saucepan. Reserve.
Pull skin off breasts, then pull chicken meat from bones. Slice meat into 3 cm strips, then crosswise to make 3 cm chunks. In bowl large enough to hold chicken, add egg white to water chestnut flour. Beat mixture with a single chopstick (not an egg beater or whisk). Stir chicken pieces into egg mixture to coat thoroughly. Marinate 5 minutes.
Note: water chestnut flour gives a lighter crust than cornstarch, though the latter may be substituted.
Deep-frying: Heat cooking oil in wok or deep-fryer to medium heat. Fry peanuts until they are a light tan color; if a test peanut browns quickly, turn down heat. Remove peanuts with strainer or slotted spoon; drain on paper towel or paper bag. Reserve. Turn up heat slightly for chicken. Test a chunk first: chicken should raise to surface immediately & brown in about 2 minutes. Deep-fry coated chicken chunks until golden brown. Deep-fry no more than 8 chunks at a time. Use long chopsticks or spatula to keep pieces separate while they are frying. Remove with long chopsticks or slotted spoon. Reserve.
Sauce: While deep-frying chicken, heat sauce to simmer. Add green onions & peanuts about a minute before serving. At the last minute, add chicken pieces to sauce, mix quickly & serve.