Finely slice the cucumber into thin discs. Finely slice the cos lettuce. Finely slice the red chilli (if using). Roughly chop the coriander. Cut the grenadier into 2cm strips.
In a large bowl, mix the cucumber with the rice wine vinegar, warm water, caster sugar and 1 tsp of salt. Mix well and set aside for 15-20 minutes, or until the cucumber is soft. Tip: Pickling is a simple way to add maximum flavour to a dish.
Combine the fish with the turmeric, a drizzle of olive oil and 1/4 tsp of salt and a pinch of pepper in a medium bowl. Toss well to coat.
Heat a large frying over medium-high heat and add in a drizzle of olive oil. Add in the grenadier pieces and cook, turning for 5-6 minutes, or until the centre of the fish is white. Once cooked, season with salt and pepper set aside on a plate covered with paper towel.
Meanwhile, heat the mini tortillas in a microwave or sandwich press until warmed through (if using a microwave, place tortillas on a plate first).
Divide the lettuce between the tortillas, top with the turmeric fish and pickled cucumber and drizzle with garlic aioli. Enjoy!