In a medium size bowl combine flour, 2 tbsp cornstarch, baking soda, baking powder and whisk. Pour in 2 tbsp soy sauce, dry sherry, 2 tbsp water, vegetable oil, and a dash of sesame oil; stir until smooth. Stir in chicken until coated with batter, cover, then refrigerate for 20 minutes.
Heat oil in a deep fryer or large saucepan to a temp. of 375 degrees. Carefully drop in the battered chicken pieces, only a few at a time and fry until they turn golden brown; about 3-4 minutes per batch. Drain on a paper towel lined plate.
For The Sauce
Meanwhile in a large skillet or wok, bring chicken broth, sugar, rice vinegar, soy sauce, sesame oil, Siracha hot sauce, and garlic to a boil over high heat. Dissolve 1/4 cup cornstarch into 1/2 cup water, and stir into boiling sauce. Simmer until the sauce thickens, about two minutes.
Add the crispy, cooked chicken pieces to the sauce and stir to coat. Sprinkle with sesame seeds to garnish. Enjoy!!