Cook the rice noodles according to instructions on the packet. Drain and transfer to a salad bowl.
Place broccoli and carrots into a steaming basket over boiling water; steam for about 5 minutes, or until it's cooked to your liking. Add to the noodles. Place sliced red pepper into the steamer and steam for 2 to 3 minutes until cooked. Add to the noodles as well.
Heat 1 tablespoon vegetable oil in a frying pan over medium heat. Add prawns and fry on all sides until they are pink on the outside and cooked through. Add garlic and fry for a few more minutes. Remove from the stove, stir in sesame oil and chilli flakes; stir into the noodles.
For the dressing: Whisk together 2 tablespoons vegetable oil, rice vinegar, lime juice, sugar, soy sauce and fish sauce in a small bowl, until sugar has completely dissolved. Pour over the noodles and toss carefully until well combined. Sprinkle with spring onions and freshly chopped coriander; serve.