Add the jalapeno pepper, scallions, mayo, lemon juice, pickling liquid, pickles, mustard, and parsley to a blender and pulse until almost smooth. (I like to leave some texture).
Season with salt and pepper to taste. Cover and chill in the fridge until ready to use.
Fry the Catfish
When ready to cook catfish, heat enough oil to fill a large Dutch oven 2 inches.
Set up your dredging station with the eggs in one dish and flour in another.
When the oil reaches 350 degrees F, work in batches coating the fish in the egg, draining excess and dredging in the flour.
Place each piece in the oil and fry for 5 to 7 minutes, until cooked through.
Remove from oil with a slotted spoon and place on a paper towel lined plate to drain.
Assemble the Sandwiches
Toast the rolls with the melted butter.
Spread the remoulade over the rolls, pile high portions of the fried fish and serve with sliced tomato, shaved celery, and sliced scallions.