Tempura sauce:

In a medium bowl, mix rice wine and salt. Add the shrimp, cover, and marinate in the refrigerator at least 20 minutes.

Heat oil in deep-fryer or large wok to 375 degrees F.

In a medium bowl, mix together all-purpose flour, ice water, cornstarch, egg yolk, salt, white sugar, and baking powder. One at a time, dip shrimp into the flour mixture to coat. Carefully place a few shrimp at a time in the hot oil and deep-fry until golden brown on all sides, about 1 1/2 minutes. Use a slotted spoon to remove the shrimp from the oil and drain on paper towels. Repeat with remaining shrimp.

Tempura sauce:

Stir together soy sauce, water, rice vinegar, and sugar until sugar is dissolved. Just before serving, stir in the scallions and serve immediately with the shrimp.