Combine the cornmeal and flour, then add the dried onion, garlic, basil, thyme, kosher salt, white pepper and cayenne pepper. Pour the mixture in a resealable plastic bag and dredge the catfish fillets, one by one.

Light a charcoal barbecue to medium heat. Place a cast iron or heavy enamel skillet on the grill rack. When it gets hot, add the butter.

When the butter has stopped sizzling, add the coated fillets, flat side up. Close the hood to the barbecue and let the fish cook, about 6 to 8 minutes. Turn the fish over and finish cooking, covered, for another 6 to 8 minutes. The fish is done when it flakes easily with a fork.

Plate the fillets on a warmed platter and pour the juices from the skillet over the fish. Serve with lemon wedges and chopped fresh parsley scattered over the top.