Special Equipment: Candy/frying thermometer, cast iron skillet
Divide the seasoned flour into two medium mixing bowls. Add the chopped pecan pieces to one of the two bowls and mix well.
In a separate bowl, beat the eggs. Add the milk, and whisk to combine.
Fill a cast iron skillet with vegetable oil until it's filled up to half an inch, then heat over medium heat. Adjust heat to maintain a temperature of 325 degrees (this is where the thermometer comes in handy).
Dredge the fish fillets in the seasoned flour without the pecans, then in the egg mixture. Repeat one or two times to develop a batter layer on the fish fillet. After the final dredge in the egg mixture, dredge the fillets in the pecan flour, pressing slightly to make sure the pecan pieces stick to the fish.
Carefully place the fillets in the hot oil and fry for about 2-3 minutes or until the pecans around the edges begin to brown. Carefully turn the fish over using a spatula and fry for another 2-3 minutes. Remove the fish from the pan, and place on a plate layered with paper towels. Once drained, serve hot.