To make the Vietnamese Dressing, simply mix all the ingredients together. This will keep very well in a tightly sealed jar in the refrigerator for at least a week.
To make the salad, marinate the shrimp in 1/2 cup of the Vietnamese Dressing. While this is going on, soak the noodles in freshly boiled water according to packet instructions. Once re-hydrated, refresh the noodles in cold water, then drain. Put the sugar snaps and bean sprouts into a colander and pour over freshly boiled water from a kettle. Rinse them with cold water and drain well, just shaking the colander, so they're not actually wet.
In a large bowl, mix the marinated shrimp with the drained noodles, scallions, sugar snaps, and bean sprouts. Dress with 2 tablespoons more of the Vietnamese Dressing; add more dressing, to taste, if desired.
Sprinkle over the chopped cilantro and toss everything together well before arranging onto a large plate.
Recipe courtesy of Nigella Lawson(Copyright 2004, Feast, Hyperion, All Rights Reserved)