1.Place the fish fillets in the food processor, then finely chop.
2.Place the fish in a bowl along with 1/4 cup panko, 1 egg, and mayonnaise, mustard, salt, onion powder, and cayenne pepper. Use a large spoon to combine.
3.Shape the fish mixture into 1 1/2-ounce finger-shaped sticks. Set on a sheet pan and refrigerate for 30 minutes to firm up.
4.Meanwhile, beat the remaining 1 egg in a shallow dish. Place the remaining panko in a second shallow dish and the flour in a third.
5.When the fish sticks are firm, roll each stick in the flour, then egg, followed by the panko and place back on the sheet pan on top of a cooling rack. Place back in the fridge. If you're not ready to cook, cover with plastic wrap and refrigerate for up to 6 hours.
6.Preheat oven to 400 degrees. Once the oven is preheated take the fish sticks out of the fridge and spray with cooking spray on top. Bake for 6 minutes, take the fish sticks out and flip to the other side. Spray on top with cooking spray again and bake for another 6 minutes. Serve immediately.