In a large bowl, mix 2 tablespoons soy sauce, 1/2 tablespoon tangerine zest, 1/4 cup tangerine juice, half of the chopped green onions, 1 tablespoon ginger, and 2 cloves of the grated garlic. Add the chicken pieces, a pinch of salt and pepper, and toss until thoroughly coated in the marinade. Cover and refrigerate for at least 1 hour.
Make the orange sauce. In a small mixing bowl, whisk the remaining soy sauce, tangerine zest, chicken stock, tangerine juice, rice vinegar, and brown sugar.
Place the cornstarch in a large bowl. Remove the chicken pieces from the marinade, dredge them in the cornstarch, and shake to remove any excess.
In a heavy-bottomed saucepot, heat the oil over medium-high heat. Working in batches and adding more oil if necessary, cook the chicken until golden brown on all sides, about 3-5 minutes. Using a slotted spoon, remove the chicken pieces from the pan and set them aside on a paper towel-lined plate. Reduce the heat to medium-low.
Add the remaining ginger, garlic, and the chilies to the oil and sauté until very fragrant, about 30 seconds. Pour in the orange sauce, scraping to remove any brown bits stuck to the bottom of the pan. Bring the sauce to a boil, reduce the heat to simmer, and cook for 5 minutes until thickened, reduced, and syrupy. Return the chicken to the pan and toss to coat. Stirring occasionally, continue to cook until the chicken is fully warmed back through, 2-3 minutes.
Transfer the chicken to a platter and garnish with the remaining green onions, tangerine wheels, and toasted sesame seeds. Serve over steamed white or brown rice and serve with extra hot sauce on the side.
