For the Batter: Whisk together flour, cornstarch, beer, egg, and salt in a medium-sized bowl. Make sure there are no lumps. Cover bowl and place in fridge for at least 20 minutes, and up to 3 hours.

For the Fish: Pour oil into a large dutch oven. Turn heat to medium and bring to a temperature of 375 degrees F.

Dry fish fillets with paper towels. Season both sides with salt and pepper. Drop each piece into the bowl of batter.

When oil is at 375 degrees F., remove one piece of fish out with a pair of tongs, letting the excess batter drip back into the bowl. Then lower it into the oil, holding on to it for a few seconds to keep it from sticking to the bottom. Repeat process with other fillets. Adjust heat to medium-high to keep temperature at about 350 degrees F. Cook until fillets are golden brown, about five minutes.

Drain fish fillets on a baking sheet covered with paper towels. Serve with cole slaw, malt vinegar, lemon, or whatever you like best.