Combine cornmeal, seasoned salt, pepper, and garlic powder in a shallow dish. Pour milk into a separate dish.
Heat oil and butter in a large skillet over medium heat.
Dip a catfish fillet in the milk, and shake off any excess. Transfer milk-soaked fish to the cornmeal mixture and gently roll to coat on both sides. Repeat with remaining fillets.
Place fish in the hot skillet and cook until golden brown on each side (about 5-7 minutes per side). The fish will flake easily with a fork when it’s done. Depending on the size of your skillet, you may need to cook the fish in batches. Don't overcrowd the skillet! Feel free to wipe out the pan and use additional butter/oil, as necessary, for subsequent batches.
Drain fish on paper towels. Serve warm, garnished with chopped fresh parsley and a lemon wedge, if desired.
Video
Notes
Shake off the excess milk and cornmeal each time you dredge the fish to make sure that you just have a light coating on each piece.
Depending on the size of your skillet, you may need to fry the fish in batches so that you don't overcrowd the pan. This will keep the oil at a steady temperature and will ensure crispy (rather than soggy) fish fillets.
Serve the fried catfish with lemon wedges and a fresh parsley garnish for a bright finishing touch.
Season the catfish with additional kosher salt and ground black pepper, if desired, while the fish is still warm.