Whisk the buttermilk and hot sauce together. Pour over the catfish pieces so they are fully submerged. Cover and refrigerate for 20–30 minutes (this tenderizes and helps coating adhere).

Prepare coatings

In a shallow dish combine the flour, cornmeal, panko, 1 tsp salt, 3/4 tsp black pepper, garlic powder, onion powder, paprika, and cayenne. In a second shallow dish beat the eggs until homogenous.

Dredge

Remove catfish from buttermilk, letting excess drip off. First lightly toss pieces in the flour/cornmeal/panko mixture to coat. Dip into beaten eggs, then return to the coating mixture for a second, thorough coat—press gently so crumbs adhere. Place coated pieces on a wire rack while you heat oil.

Heat oil

Pour vegetable oil into a heavy-bottomed skillet or deep pot to a depth of about 1 to 1 1/2 inches (about 2–3 cups depending on pan). Heat over medium-high until the oil reaches 350°F (175°C) or until a small pinch of coating sizzles and browns in ~30 seconds.

Fry

Fry the catfish bites in batches (do not crowd) for 2–3 minutes per side, turning as needed, until golden brown and internal temperature reaches 145°F (63°C). Use a slotted spoon to transfer bites to a wire rack set over a sheet pan or to paper towels to drain. Sprinkle immediately with remaining 1/2 tsp salt while still hot, if desired.

Keep warm

If needed, keep cooked batches warm in a 200°F (95°C) oven on a wire rack while finishing remaining batches to maintain crispness.

Serve

Serve the popcorn catfish hot with lemon wedges and the house tartar sauce for dipping.

House Tartar Sauce

Combine the mayonnaise, diced dill pickle, minced shallot, chopped capers, lemon juice, Dijon mustard, chopped parsley, sugar, salt, and black pepper in a small bowl.

Taste and adjust: add more lemon juice for brightness, sugar or a pinch more salt to balance. Chill at least 10 minutes to let flavors meld (longer is better). Stir before serving.