Our take on this classic British pub grub is just right. Rice flour, baking powder and beer in the batter keep the breading light and crisp, and making your own "chips" is definitely worth it. The double-frying method at two different oil temperatures ensures that the potatoes are perfectly golden and never soggy.
Set a colander in a large bowl of ice water. Slice the potatoes lengthwise 1/4 inch thick, then stack the slices and cut into 1/4-inch-thick sticks, adding them to the ice water as you work. Refrigerate 30 minutes or up to 1 hour. Lift the colander out of the ice water, rinse the potatoes well and pat very dry.
Preheat the oven to 350 degrees F. Heat 4 inches vegetable oil in a large Dutch oven until a deep-fry thermometer registers 280 degrees F. Add half of the potatoes; fry until tender but still colorless, about 5 minutes. Remove with a slotted spoon to a paper towel-lined plate. Repeat with the remaining potatoes. Increase the oil temperature to 365 degrees F.
Whisk 3/4 cup all-purpose flour, the rice flour, baking powder, 1 teaspoon salt and the cayenne in a large bowl. Whisk in the beer until mostly smooth. Let sit 5 minutes to thicken.
Set a wire rack on a rimmed baking sheet. Season the fish with salt. Working in two batches, dredge the fish in the remaining 1/2 cup all-purpose flour, then dip in the beer batter, letting the excess drip off. Fry until crisp and golden brown, about 4 minutes. Transfer to the rack; sprinkle with salt. Keep warm in the oven.
Increase the oil temperature to 380 degrees F. Working in two batches, fry the potatoes again until crisp and golden brown, about 2 minutes. Drain on a paper towel-lined plate and season with salt. Serve the fish and chips with malt vinegar and lemon wedges.