Shred the cabbage and toss in a large bowl with the lime juice, honey and salt. Set aside.
Mix all the ingredients for the mayo and set aside.
Season the cod with salt and pepper.
In a large bowl, make the batter for the cod. Whisk the flour, corn starch and salt together and slowly add in the club soda, stirring until smooth.
In a saucepan, heat 3 inches of vegetable oil to 350 degrees, checking the temperature with an oil thermometer.
Dip the cod slices into the batter then gently place in the oil. Work in batches of two at a time so as not to crowd the pan or lower the temperature of the oil. Fry for about 5 Minutes, flipping a couple times until golden brown. Place the cod on a cooling rack to drain and sprinkle with a pinch of salt.
Heat the tortillas over an open flame on the stove, flipping to make sure they don't burn, until slightly charred and bubbly.
Assemble the tacos as follows: Tortilla, fried cod, cabbage, avocado slice, drizzle of mayo, cilantro or parsley, and a squeeze of lime.
Devour immediately!