From America's Test Kitchen Season 10: Classic Asian Appetizers
A few preliminary attempts at making tempura made us see why some Japanese chefs devote their entire careers to this one technique. Success hinges almost entirely on the batter—which is maddeningly hard to get right. We wanted a recipe for perfectly cooked shrimp tempura—light, crisp, and so fresh-tasting that it barely seemed fried.
We settled on using the largest shrimp available, since it’s easy to overcook small shrimp. Instead of a wok, we substituted a large Dutch oven, the test kitchen’s preferred deep-frying vessel. Cooking the tempura in 400-degree oil also helped limit grease absorption. To prevent the batter from clumping on the inside curl of the shrimp, we made two shallow cuts on the underside of its flesh. For the batter, we replaced a bit of the flour with cornstarch to improve the structure and lightness. For a super tender coating, we used a combination of seltzer and vodka instead of the traditional tap water. Seltzer is a little more acidic than tap water and therefore slows down gluten development, while the vodka prevents the formation of gluten. Our tempura was now light and crisp with the essence of sweet, tender shrimp.
Do not omit the vodka; it is critical for a crisp coating. For safety, use a Dutch oven with a capacity of at least 7 quarts. Be sure to begin mixing the batter when the oil reaches 385 degrees (the final temperature should reach 400 degrees). It is important to maintain a high oil temperature throughout cooking. If you are unable to find colossal shrimp (8-12 per pound), jumbo (16-20) or extra-large (21-25) may be substituted. Fry smaller shrimp in three batches, reducing the cooking time to 1½ to 2 minutes per batch. See Straighten Out Your Shrimp below for tips on preventing the shrimp from curling.