Place the chicken in a bowl and sprinkle the soy sauce over it.
Cover and refrigerate for 1 hour.
Sift together the flour and cornstarch into a bowl.
Whisk in the egg and water until smooth.
Let the batter stand for 10 minutes.
Pour oil to a depth of 50mm into a deep fryer or wok and heat to 180 degrees C over medium heat.
Working in batches, dip the chicken in the batter and gently shake off the excess.
Deep-fry the chicken, a few pieces at a time, until light golden and cooked through, 4-5 minutes.
Reduce the heat if the chicken browns too quickly.
With a slotted spoon, remove the chicken to drain on paper towels.
Cool to warm or to room temperature.
Before serving, place the chicken in a serving bowl and gently toss with the desired amount of Chilli Sauce, lemon juice and coriander leaves.