Combine flour, cornmeal, baking powder, mustard, and salt in a medium mixing bowl; stir well. Combine milk and egg in a small mixing bowl; add to dry ingredients, stirring well. Set aside.
Wipe each frankfurter dry, and insert a wooden skewer into one end. Dip frankfurters in batter; fry in deep hot oil (375° to 400°) for 3 minutes or until browned, turning once. Drain well on paper towels. Repeat with remaining frankfurters. Serve with mustard and catsup, if desired.