Prepare a fish dredging station with two bowls. One bowl should contain a splash of milk mixed with a beaten egg. The second bowl will contain all purpose flour, cayenne pepper, salt, pepper and paprika all mixed together.
Dry off your fish fillets very well. Using one fillet at a time, place in the flour mixture and thoroughly coat the fish, pressing the flour into all surfaces and any crevices on all sides.
Transfer the floured fish into the egg/milk mixture and make sure it gets wet and coated on all sides.
Then place the fish back into the flour mixture and make sure there are no visible areas where egg/milk shows through. Press flour into the fish very well, coating all around.
Repeat for all of your fish fillets and let each one rest after dredging on parchment or a baking rack while your frying oil comes to temperature.
In a large pot or skillet add peanut oil until it fills at least 2 inches deep in the vessel. On medium high heat bring oil up to 350 degrees. If you do not have a thermometer, heat the pot over a burner for a few minutes and sprinkle a tiny bit of flour in the oil. If it starts to bubble as soon as the flour hits the oil it should be hot enough (make a mental note that you should get a thermometer).
Add each fillet into the oil, making sure to ease it in away from your body so that you do not splash yourself with hot oil.
Fry in the oil for 3 minutes per side or until the crust of the fish is nice and golden brown. Once the fish is all done, move it to a plate or cooling rack to rest.
In a seperate smaller skillet, add your butter, hot oil, cayenne pepper, brown sugar, paprika and garlic powder. Turn on medium heat and cook, stiring frequently until everything is combined and your butter is melted.
Place each fish fillet into the sauce one at a time and flip until it is coated.
Move your fish fillets onto buns or bread. If you'd like you can spoon any extra sauce over the fish for extra heat. Enjoy with pickles.
Notes:
This is a very spicy sandwich. To control the spicing, you're going to have to reduce the cayenne in the sauce. The cayenne in the flour dredge only adds a tiny bit of spice.