To make the sauce: Mix all ingredients in a bowl and refrigerate until serving.
When ready to fry, fill a large heavy pot with enough oil to measure 1 1/2 inches up the side of the pan and heat to 350 degrees F.
To make the catfish sticks: In a measuring glass, mix together 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. Meanwhile place flour in a shallow bowl. Combine the bread crumbs with sugar and place in another shallow bowl. Remove fish from the buttermilk mixture and coat lightly with flour. Place strips back in the buttermilk and then dredge in the bread crumb mixture. Fry strips in batches for about 3 minutes on each side or until golden brown. Drain on a paper towel-lined plate.
Serve catfish sticks with dipping sauce.