1 cup buttermilk, cold
1 teaspoon kosher salt
1 teaspoon freshly ground black pepper
½ cup cornstarch
½ cup tapioca flour (also know as tapioca starch)
4 each (4 ounce) tilapia fillets
1 – 2 cups canola oil
4 lemon wedges
Season both sides of the fillets with salt and pepper.
Place the buttermilk in a 2-inch deep container that is large enough to fit the 4 pieces of fish.
Season the buttermilk with salt and fresh ground pepper.
Sift the cornstarch and tapioca together into another baking dish that is large enough to fit the fillets.
Place tilapia fillets in buttermilk, coating them all around. Leave to marinate for 15-20 minutes, but note that the acid in the buttermilk will start cooking the fish if left too long.
Remove the fillets from the buttermilk, one at a time, draining off any excess and place them in the flour mixture. Coat fillets well on all sides by flipping them in the flour mixture several times all sides. Move to rack.
Heat a large heavy-bottomed sauté pan over medium-high heat and add the oil. It should be enough oil to cover the bottom of the pan by ¼ inch.
Once the oil is very hot (it should look liquid and be shimmering, almost smoking but not quite), add the fillets and color lightly until golden brown and crisp, about 2-3 minutes. Note: Do not overcrowd your pan. There should be approximately 2 inches around all of the fillets. If there is not enough room in your pan, cook the tilapia in batches. Additionally, make sure to use a nonstick pan and allow the oil to heat up long enough so that it is super-hot before placing the fish in the pan. Avoid dripping any water into the oil as it will make the oil splatter as you cook.
Gently turn fish over and cook until the other side is golden brown and crispy, about another 2-3 minutes. Make sure to flip the fish away from you to avoid oil splattering. At this point, see if the fish is cooked through by inserting a cake tester into the center. If it comes out warm to the touch, the fish is done. If it still feels cool, transfer the fish to a baking sheet lined with a rack and place in the oven. Finish cooking in the oven as needed. The cooking time will depend on how thick the fillets are. Test with a cake tester every 2-3 minutes. When the center is warm to the touch, remove from the oven. Drain on rack or plate with paper towels. Serve with wedges of lemon.