First, make the dressing in a bowl. Make the slaw by shredding the cabbage and onion, and mix with HALF the dressing. (Save the rest of the dressing.)
Add the oil to a hot, large frying pan. Add the prawns, then spices, and cook for 5 minutes.
Toast the tortillas (see notes), then add the slaw and prawns on top with the avocado slices.
Serve with extra dressing drizzled on top.
Notes
Toasting the tortillas: Hold very carefully over an open flame on a gas hob with tongs. Alternatively, fold over the tortillas and put into the toaster slots, or you can pop in the oven for three or four minutes instead.