Add 1 tbsp oil to the wok. Finely grate the ginger and mix with the fish sauce, chilli sauce, lime juice and remaining oil. Stir-fry the prawns for 4-5 minutes.
Remove from heat and add the sauce. Put the noodles in a large bowl. Halve the cucumber lengthways and slice thickly, coarsely grate the carrot, and slice the chilli and the onion.
Add to the noodles along with the fresh herbs. Mix in the prawns, toss well and serve.
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