Split the shrimp down the middle and put them, split side up, in a bowl. Chop two of the chilies and half the ginger. Add half the vegetable oil to the chopped chili and ginger. Pour this over the shrimp and mix well.
Place the shrimp cut side down on a hot griddle pan. Turn the shrimp 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 to the cooked rice noodles.
Cut the remaining ginger and chilies into fine strips and add them to the noodles. Season to taste.
For the dipping sauce, mix two tablespoons of sweet chili sauce with the passion fruit juice and one teaspoon of lime juice.
Serve on a large platter, with the noodles on one end and a stack of shrimp on the other, with the dipping sauce in a small dish in the middle.