Combine the water, vinegar and sugar into a small saucepan on a medium heat while stirring. Once the sugar has dissolved, pour the hot liquid over the thinly sliced red onions and set aside to pickle for 5-10 minutes.
In a small bowl combine the crushed cornflakes, flour and pinch of sea salt. In another small bowl combine the egg and a dash of milk and lightly beat using a fork.
Heat up a fry pan on a medium heat, 1cm deep with vegetable oil.
Slice up the fish fillets into strips, coat in the egg wash then coat in the cornflakes. Place in the oil once it has heated up to frying point – be careful it’s not too hot. Using tongs gently turn the fish over once a nice golden colour develops. Fry on the other side before removing and placing on a paper towel to absorb any excess oil.
Repeat the process until all the fish is cooked.
Combine all the salsa ingredients into a serving bowl and toss to coat. Set aside.
Combine the Greek yogurt and hot sauce in a small dish, stir well to combine and set aside.
Warm up the taco shells according to the packet instructions.
Serve the fish, salsa, quick pickles and toppings on the table so your everyone can build their own taco.