In a small bowl, combine the mayonnaise, Creole mustard, horseradish, paprika, Cajun seasoning, Worcestershire sauce, parsley, minced garlic, lemon juice, and a pinch of cayenne pepper. Mix well, cover, and refrigerate until needed.

Slice the catfish fillets into 1-inch strips and place them in a medium bowl.

In another bowl, whisk together the buttermilk, egg, and Cajun seasoning. Pour over the catfish strips, cover, and refrigerate for at least 30 minutes (up to 2 hours).

In a pie plate, whisk together the flour, cornmeal, and salt.

In a Dutch oven or deep cast iron skillet, pour in enough vegetable oil to cover the bottom by a couple of inches. Heat the oil to 350°F to 365°F.

Remove the catfish from the marinade, let the excess drip off, then dredge the catfish strips in the flour-cornmeal mixture.

Carefully place the catfish in the hot oil, frying in batches to avoid overcrowding. Fry for about 3 to 4 minutes on each side until golden brown.

Transfer the fried catfish to a paper towel-lined plate or a wire rack.

Serve immediately with the chilled Cajun remoulade on the side.