Pour enough vegetable oil into a wok to half fill the wok. Heat over high heat. Toss chicken in combined flours, spice, salt and chilli until coated. Deep-fry chicken, in two batches, for 3-4 minutes or until crisp. Transfer chicken to a plate lined with paper towel.
Discard vegetable oil. Wipe wok clean. Add sesame oil to wok and heat over high heat. Cook garlic, ginger, choy sum and snow peas for 2-3 minutes or until vegetables are just tender.
Return chicken to wok with combined sauces. Stir-fry for 2 minutes or until heated through. Serve stir-fry on steamed rice.