Soak the rice noodles in boiling water for 10 minutes and drain.
Heat wok to high heat. Add vegetable oil and swirl to coat wok.
Lower heat to medium high and add mushroom and garlic and stir-fry till fragrant. Add prawns and cook for a minute.
Add pepper and pak choy. Stir-fry for another couple of minutes.
Pour in sauce mix and stir-fry all the ingredients for a good coating.
Add water on to sides of wok to deglaze and cook over high heat for 30 seconds. Remove from heat.
Serve prawns and vegetables on the rice noodles.