Rinse and de-vein the mantis prawns. Sprinkle combined seasoning ingredients on the prawns and toss well, then coat with self-raising flour. Deep-fry in hot oil until golden brown. Dish out and leave aside.
Heat oil and sesame oil in a clean wok and fry garlic and cili padi until fragrant.
Add sauce ingredients and bring to a boil. Reduce the heat and simmer until sauce is reduced.
Return the fried mantis prawns to the wok. Stir and fry until well coated with the sauce. Add spring onion to mix. Dish out and serve.