Heat oil in a wok or large skillet over high heat until very hot.
Add onion, garlic and red pepper flakes and cook, stirring frequently, until onion is just tender but not brown. Add chicken and cook, stirring until it looses its pink color and onions start to brown. Stir in fish sauce, lime juice, brown sugar and 1/3 – ½ cup water. Cook until chicken is just cooked and juicy and liquid reduces to the consistency of a sauce. If water reduces before the chicken is cooked, add more water, 1 tablespoon at a time. Season to taste. Once chicken is cooked remove wok or skillet from the heat and add basil and stir to wilt it.
More stir fry recipes:
Sauteed mushroom with Teriyaki sauce
Pork tenderloins in pear and mustard sauce
Pasta with stir fry vegetables and Chinese black beans