Remove the muscle on the outside of each scallop and rinse the
scallops in cold water; drain thoroughly. Pat the scallops dry with
paper towels. In a medium bowl, mix ½ teaspoon salt, the
pepper, sesame oil, egg white, and 1 tablespoon cornstarch. Stir
in the scallops, cover, and refrigerate for 30 minutes.
In a small bowl, mix together 1 tablespoon cornstarch, 1 tablespoon
water, and the dark soy sauce and set aside. In a small saucepan
over medium heat, heat 1 tablespoon vegetable oil and the garlic.
Cook until the garlic is fragrant. Add the chicken broth, vinegar,
sugar, and ¼ teaspoon salt and cook to boiling. Stir in the
cornstarch mixture and return to boiling. Remove from the heat.
Heat 4 cups vegetable oil, 1 ½ inches deep, in a wok to
350°F. In a medium bowl, mix ½ cup water, the flour,
the remaining ¼ cup cornstarch, the remaining 1 tablespoon
vegetable oil, the baking soda, and the remaining ½ teaspoon
salt. Stir the scallops into the batter until well coated. Fry 8
scallops at a time for 2 minutes, or until light brown, turning
occasionally; drain on paper towels. Continue until all the scallops
are cooked. The scallops can be cooked to this point ahead of time.
Increase the oil temperature to 375°F. Refry the scallops for
about 1 minute, or until golden brown; drain on paper towels. Meanwhile,
reheat the garlic sauce and gently mix with the scallops. Garnish
with the diced green onions and serve immediately.