cook's illustrated shrimp tempura with dipping sauce

1/4 cup soy sauce
3 tbsp mirin
1 tsp sugar
1 tsp sesame oil
1 clove garlic
minced or pressed, about 1 teaspoon
2 tsp ginger
1 whole scallion
finely chopped
3 qt vegetable oil
1 1/2 cups flour
all purpose, unbleached
1/2 cup cornstarch
1 whole egg
1 cup vodka
1 cup seltzer water
1 1/2 lbs shrimp
colossal size (8-12 per pound), peeled, deveined, keep the tails on
kosher salt
portobello mushroom
This is THE way to make shrimp and veggie tempura. The folks over at Cook's Illustrated are brilliant! With the use of vodka to help ensure lightness, the fried tempura coating turned out perfect. This recipe yields more batter than needed, so we usually fry up some portabello mushroom strips with the remaining batter. This recipe will leave you with a pretty big mess to clean, but it's so worth it!
Prepare the dipping sauce by combining the soy sauce, mirin, sugar, sesame oil, garlic, ginger, and scallion. Reserve.
Adjust the oven rack to the upper-middle position and heat oven to 200°F. Heat the oil to 385°F. Heating on high, this will take about 18-22 minutes. Line the baking sheet with the parchment paper. Set the wire rack on top of the parchment paper.
In addition to shelling and deveining the shimp, cut 2 small slits about an inch apart on its underside and bend it in the opposite direction to help straighten out the shrimp.
In 2 separate bowls, whisk the flour and cornstarch together in one bowl, and combine the egg and vodka together in the second bowl. Then whisk the seltzer water into the egg mixture.
When the oil comes up to temp, pour the liquid mixture into the bowl with the flour mixture. Whisk gently until combined; small lumps are OK.
Fry the shrimp in two batches. Submerge half of the shrimp into the batter. Pull each individual shrimp out, allow excess batter to drip, then place in the hot oil. Repeat for each shrimp. Fry for 2-3 minutes until light brown. Transfer shrimp to a paper towel-lined plate, season with kosher salt while still hot, then keep warm on top of the wire rack in the oven.
When the oil temp raises back up to 400°F, fry the second batch of shrimp. Repeat with portobello mushrooms if using.
Serve all the tempura immediately with the sauce.