Heat the oil over high heat until it reaches 180°C.
In a bowl, whisk together the flour, baking powder, salt and cayenne pepper. Whisk in the beer until the batter is completely smooth and free of any lumps. Refrigerate for 15 minutes. Note: The batter can be made up to 1 hour ahead of time.
Lightly dredge fish strips in cornflour. Working in small batches, dip the fish into the batter and immerse in the hot oil. Cook until golden brown, about 4 minutes. Drain the fish on a wire rack set over a baking sheet.
