Combine the avocado dressing ingredients in a blender. Pulse until evenly incorporated.
Toss the slaw ingredients together in a bowl & set aside.
In a medium bowl, mix together the flour, salt, pepper, paprika & chilli powder. Pour the milk into another bowl & place the fish pieces in it.
Pour the corn oil into a large frying pan over medium heat. Once the oil is very hot, remove the fish pieces from the milk & dredge lightly in the flour mixture. Add the butter to the pan. Place a couple of fish pieces in the pan, without overlapping them. Fry until golden brown on 1 side, approx. 3 minutes & flip on other side & cook for 1 min. Remove & place on a plate with paper towels to absorb excess oil. Repeat with remaining fish pieces.
Warm the tortillas in a skillet over medium heat.
To serve, distribute the fish evenly between the tortillas. Top with the cabbage slaw & a spoonful of the avocado chilli sauce.