Defrost catfish if frozen, then wash and pat dry using a paper towel. Slice them into 1-inch chunks, and try to cut them uniformly sized so they cook evenly. Transfer fish to a shallow plate and set aside.
In a small mixing bowl, combine seasoning; garlic powder, onion powder, cayenne pepper, Creole seasoning, Italian seasoning, salt, and pepper. Mix well. Season fish with 2 teaspoons of the seasoning mix and thoroughly coat all slices. Set aside.
Prepare 3 small shallow bowls. Add flour in the first bowl, whisk the buttermilk and egg thoroughly in the second bowl, and mix the cornmeal and remaining seasonings in the third bowl. Arrange them in order for easy coating.
Working in batches, dredge the fish nuggets in the flour to coat (shake off excess), dip them in the buttermilk and egg mixture (let excess drip back into the bowl for a second or two), and then in the seasoned cornmeal mixture, ensuring they are completely coated.
Shake off excess cornmeal mixture, then place the catfish nuggets on a plate in a single layer while you finish breading the rest. Let them sit for 2-3 minutes to help the cornmeal mixture stick to the fish.
Heat about an inch of oil over medium-high heat in a large deep frying pan.
When the oil reaches 350℉/177℃, place a few catfish nuggets in using tongs (don't overcrowd the pan so the oil stays hot for perfectly crispy nuggets). Fry until golden brown and crisp, and the fish is cooked through, 3-4 minutes on each side. Repeat until all catfish nuggets are fried.
Transfer fried nuggets to a paper-towel-lined plate to drain excess oil. Allow to cool for about 2 minutes, then serve immediately with ranch dip, ketchup, or your favorite dipping sauce.