Prepare corn muffin mix according to package directions; set aside. Place 3 hot dogs inside a well-greased cast-iron hot dog cooker or square pie iron. Pour enough batter to fill the bottom of the cooker. Close cooker; turn over and cook over a grill or campfire 3 minutes. Turn over; cook an additional 3 minutes or until cornbread is set. Repeat with remaining batter and hot dogs. Slice between hot dogs to serve.