Combine all marinade ingredients in a gallon zip top bag or large bowl, marinade chicken for 30 minutes in the fridge.

Place cornstarch in a shallow dish or pie plate and dredge the chicken, until lightly and completely covered.

Using a whisk, combine the cold, dry tempura ingredients with the egg whites, it will be lumpy at first, but keep whisking and it will come together. Batter should be the consistency of pancake batter.

Line a large sheet pan with paper towel and place a wire baking rack on top, set next to the stove to create a frying station. In a large, heavy bottom dutch oven or deep fryer, heat the oil to 350℉, dip a small batch of the chicken in the tempura batter, drop into the hot oil and fry until golden brown, about 2-4 minutes. Do not crowd the pot. Drain the chicken on the prepared wire rack. Repeat this process until all of the chicken has been cooked.

Heat oil to 390℉ for a second fry. While oil is heating, combine all sauce ingredients in a saucepan, whisking to combine, bring to a boil and then reduce to a simmer for about 5 minutes or until the sauce is slightly thickened.

Working in two batches, drop chicken pieces into 390℉ oil until deep golden brown, about 2 minutes. Drain on the wire rack lined sheet pan. Repeat with second batch. Toss chicken in half of the sauce in a large mixing bowl. Serve immediately with rice and remaining sauce. Garnish with green onion and more sesame seeds.