In a large skillet, heat oil over medium-high heat. When the oil is very hot (it will shimmer), add the chicken. Cook, stirring occasionally, until it is golden brown and cooked thru, about 7 - 10 minutes.
In a small bowl, stir together Ponzu, honey, vinegar,red pepper flakes,ginger, garlic and sesame oil until well combined. Pour the sauce into the skillet over the chicken, and stir to coat the chicken with sauce. Bring the sauce to a boil.
In a small bowl, combine cornstarch with 2 tablespoons of water to make a slurry. While stirring, add to the boiling sauce and continue to boil for 1 minute until the sauce has thickened and the chicken is coated.
Remove pan from the heat. Serve chicken over a bed of rice, and sprinkle with sesame seeds and green onions.