Combine onion and jalapeno in a medium bowl. Bring the vinegar, lime juice, sugar and salt to a boil in a small saucepan then pour the vinegar mixture over the onion mixture allowing to stand for at least 30 minutes. (This mixture can be made and refrigerated up to 2 days in advance).
Once the onion mixture has had a chance to stand for the minimum required time, drain ¼ of the pickling liquid and toss with the cabbage, salt and pepper in a bowl.
Whisk all of the ingredients together. The sauce can be made up to 2 days in advance.
Cut fish and pat dry. Dredge each fish strip first into flour, and then dip into the egg mixture and then coat with the panko mixture. Place on a parchment lined baking sheet in one layer and bake at 350 degrees F for 20 minutes. Remove the pan, flip the fish over and return the fish to the oven for an additional 5 minutes.
Divide the fish evenly among the tortillas. Top with pickled onions, cabbage, white sauce and salsa verde.
Hint: Bread the fish with the Panko crumbs just prior to baking to ensure a crisp texture.