Most pollock, the fish preferred for this recipe, are caught by commercial trawlers using nets, but some chefs are starting to look for line-caught fish, which are more carefully caught and processed by fisherman like Tim Rider, for a superior product. Chef Jeremy Sewall uses line-caught pollock for fish and chips at Row 34 in Boston because it is a firm fish that remains flaky when cooked. The beer batter should coat this fish without being too thick; when fried, the batter should puff and crisp while the fish steams inside the crispy shell.
How to Make It
Place egg yolks in a food processor; add vinegar, Dijon, salt, and garlic. Process until blended, about 90 seconds. With processor running, slowly add canola oil and olive oil, processing until mixture is the consistency of loose mayonnaise, about 2 minutes. (The aioli should slowly drip from a spoon.) Cover and chill 2 hours.
Place 2 cups all-purpose flour in a large bowl. Stir in rice flour, cornstarch, baking soda, 2 teaspoons salt, and baking powder. Gently add beer and sparkling water, and stir until batter is smooth. (If batter is too thick, stir in additional sparkling water until consistency of thick pancake batter is reached.)
Heat canola oil to 350°F in a large high-sided skillet over medium-high. Pour buttermilk into a shallow dish, and place remaining 1 cup all-purpose flour in a second shallow dish. Sprinkle fish with pepper and remaining 1 teaspoon salt. Working with one piece of fish at a time, dip fish in buttermilk. Shake off excess buttermilk, and then dredge in flour. Shake off excess flour. Dip fish in beer batter, coating each piece completely, and let extra batter drip off fish. Using tongs, dip each piece of fish about halfway in hot oil, and cook until fish starts to float, about 6 seconds. (This prevents it from sticking to the pan and other pieces of fish.) Release fish, and fry, turning occasionally with tongs, until crispy and golden brown and internal temperature of fish reaches 140°F, about 3 minutes. Remove from oil, and place on a paper towel to drain. Sprinkle immediately with salt and pepper. Serve with malt vinegar aioli and lemon wedges.