Mix all of the ingredients in a bowl and refrigerate until serving.
For the catfish sticks:
1) In a measuring glass, mix together the buttermilk, eggs, cayenne, salt and pepper. Pour into a large plastic bag, then add the catfish. Seal, removing as much air as possible, and refrigerate for 10 minutes.
2) Fill a large heavy saucepan with enough oil to measure 4cm up the side of the pan and heat to 180C.
3) Meanwhile, place the flour in a shallow bowl. Combine the breadcrumbs with the sugar and place in another shallow bowl. Remove the fish from the buttermilk mixture and coat lightly with the flour. Place the strips back in the buttermilk and then dredge in the breadcrumb mixture. Fry the strips in batches for about 3 minutes on each side or until golden brown. Drain on a paper towel-lined plate.
4) Serve the catfish sticks with the dipping sauce.