In a medium mixing bowl blend flour, cornmeal, salt, and pepper together. In a separate medium mixing bowl beat egg well, add beer and minced onions, mix well.
Cut the catfish into 2 inch cubes or strips. Heat the vegetable oil. Roll the catfish into the flour mixture, then dip into the beer-egg mixture, then back into the flour mixture. Place flour and dipped catfish into the deep-fry, cook until golden brown.