Check your avocado is ripe before starting. (To speed up ripening, put avocado in a paper bag with a banana, close loosely and leave on the bench for a day or two.) Preheat oven to 180C, fan-forced. Line a large oven tray with baking paper. Thinly slice half the onion*. Thinly slice the cabbage using a sharp knife or mandoline. Coarsely chop the coriander leaves and finely chop stems.
Step 2 — Bake seasoned tortillas
Combine the Spanish seasoning, 1 tsp dried oregano and 2 tbs olive oil in a large bowl and season with salt and pepper. Put the tortillas in a single layer on the lined tray and brush with three-quarters of the seasoned oil. Reserve the remaining seasoned oil in the bowl. Bake the tortillas for 13-15 mins until golden. Cool.
Step 3 — Pickle onion
Meanwhile, put the onion and 1 tsp dried oregano* in a large heatproof bowl. Put 1½ tbs white wine vinegar, 1 tsp sugar and a large pinch of salt in a small saucepan and bring to the boil. Pour over the onion mixture and set aside to pickle, tossing occasionally, until needed.
Step 4 — Make guacamole
Finely grate the zest of half the lime, then juice the whole lime. Scoop the avocado into a bowl. Add the lime zest and coarsely mash with a fork. Stir in the coriander stems and 1 tbs lime juice and generously season with salt and pepper.
Step 5 — Cook prawns
Add the prawns to the reserved seasoned oil and stir to coat. Heat a medium frypan over high heat. Cook the prawns, stirring, for 2-3 mins until just cooked through.
Step 6 — Get ready to serve
Add the cabbage and 2 tsp extra virgin olive oil to the pickled onion mixture, season with salt and pepper and toss to combine. Arrange the prawns, baked tortillas, guacamole, cabbage mixture, salsa and coriander leaves on a serving platter and serve at the table.