Place jalapeños, pickling liquid, coriander and green onion into a small food processor and process till coarsely chopped.
Peel and devein the prawns, leaving the tails intact or remove if desired.
Place half of the salsa into a bowl, add the prawns and toss to combine. Refrigerate until ready to serve.
Place the onions and vinegar into a bowl and season with salt and pepper, toss to combine. Refrigerate for 30 minutes.
Divide the cabbage and prawns between the tortillas, top with pickled onions, coriander and fresh lime juice.
Serve with extra pickled jalapeño salsa.