Preheat a cast iron skillet over medium heat with about 1/2 inch oil. I used a Mediterranean blend of sunflower and olive oil.
Go ahead and have three bowls laid out. You want one for your dredging mix, one for your egg mixture, and one for your breading. It should be a little assembly line leading to your skillet.
The dredging mix I used was simply 1 cup of flour. You can add salt and pepper here (along with any other seasonings) or wait to add it in the breading bowl, like I did. The word dredge used here means to lightly coat a food with a dry ingredient. You'll want to coat every nook and cranny with this before you go on to the egg bowl.
The egg mixture is the second station for your fish to visit before it goes to the pan. I whisked together 2 eggs, a splash of milk, and 1 tbsp of apple cider vinegar. After you dredge it in flour, you'll want to coat it in the egg mix before it gets breaded.
The breading is where it all comes together before it goes into the hot oil. This will give you a nice crispy, crunchy bite of fish. So for the breading I mixed 1 cup of panko breadcrumbs, 1 tspn ground black pepper, 1 tspn garlic powder, 1 tspn onion salt, and 1/2 tspn of basil. Mix everything together well. I mixed mine in a Ziploc bag first so I could crush those breadcrumbs up a bit. When it's good, pour them into your bowl, and line them all up in order to make it easier. Once you start frying you'll want your focus to be on that fish in the skillet.
When your oil is nice and hot, back the heat off one notch. I always do this because once cast iron warms up, it gets hot and maintains that heat really well. So by backing the heat off a notch, I get the perfect temp for most things.
I cut my fish into about 1-2 inch wide strips. Take your strips and run them through the stations. Make sure they get coated nicely in each bowl. Then gently lay them in your hot oil.
You shouldn't have to worry about these bringing your heat down any. I didn't have any issues. But don't get too far ahead of yourself. Work with as much fish cooking at one time as you can handle. Cook each side until browned (about 3 minutes per side).
When they're done, transfer them to a cooling rack to drain the grease off. Don't put them straight onto paper towels or anything, that will make them get soggy. Letting them dry on a rack allows the air to help that breading harden up everywhere. That's what gives you a nice crunchy piece of fish. Once they're all cooked and have dried on the racks for a few minutes, you can place them in a basket or bowl to be served up.
Assemble your tacos, top with shredded cheese and your other toppings, and enjoy!