Beat the egg, then beat in beer. Whisk in the flour, salt and pepper until smooth. Cover and let stand 30 minutes. Just before frying, stir in the baking powder. Preheat the oil to 180°C. Cut fish into serving size pieces and pat dry with paper towels. Dip into flour and then batter. Lower into hot oil and fry about 3 minutes or until golden brown and puffy. Drain. Approximately 4 servings.