Split the prawns down the middle and put them, split side up, in a bowl.
Chop two of the chillies and half the ginger. Add half the vegetable oil to the chopped chilli and ginger. Pour this over the prawns and mix well.
Place the prawns cut side down on a hot griddle pan. Turn the prawns after two minutes. At this point, pour half the lime juice and zest over them and leave to cook for another two minutes.
Meanwhile, make the noodle salad. Add the shredded pak choi, coriander, sesame oil, a splash of vegetable oil, the remaining lime juice (reserving one teaspoon) and zest and the peanuts to the cooked noodles.
Cut the remaining ginger and chillies into fine strips and add them to the noodles. Season to taste.
For the dipping sauce, mix two tablespoons of sweet chilli sauce with the passion fruit juice and one teaspoon of limejuice.
Serve on a large platter, with the noodles on one end and a stack of prawns on the other, with the dipping sauce in a small dish in the middle.