To prepare the blueberry and nashi salsa: Combine nashi, blueberries, coriander and mint in a medium bowl. Add the lime juice and toss to combine. Set aside.
To prepare the creamy avocado sauce: Place the avocado, red onion, coriander, garlic and cumin in a small food processor and blend to make a thick puree. Add the lime juice and olive oil and blend until smooth. Season with salt and pepper.
Cut the fish into 1 ½cm thick strips, approximately the width of the tortillas. Combine the arrowroot, paprika, cumin and salt in a medium bowl. Add the fish and toss to coat.
Preheat a large frying pan over medium heat.
Drizzle the pan with olive oil. Cook the fish for 1 minute, on each side, or until just cooked through.
At the same time, cook the tortillas in a dry hot cast iron or non-stick pan for 10 seconds on each side, or until hot and lightly toasted. Stack and cover with a clean tea towel to keep warm.
To assemble, fill the warmed tortillas with avocado and jalapeno sauce, shredded cabbage, fish and salsa.