Season chicken with salt and pepper. Heat oil in a large skillet over medium high heat. Add chicken and cover skillet for 5 minutes. Stir chicken and cover for 2-3 minutes more or until chicken is no longer pink.
Reduce heat to medium. Whisk remaining ingredients in a bowl and pour into pan. Stir to coat chicken with sauce and cover for 4-5 minutes or until mixture is boiling.
Once boiling remove cover and continue to stir until sauce thickens, about 2-3 minutes.
Top with scallions and sesame seeds. Serve with roasted broccoli and/or cauliflower rice.