Whisk together orange juice, zest, chicken broth, soy sauce, honey, rice vinegar, and chili flakes in a medium-sized bowl.
Whisk together 2 teaspoons cornstarch with 4 teaspoons water in a small bowl to make a cornstarch slurry.
Mince 1 tablespoon garlic and 1 tablespoon ginger. Set aside.
Cut the chicken breast into 1-inch cubes. In a medium bowl, combine 1 teaspoon kosher salt, ½ teaspoon pepper, and ½ teaspoon sesame oil.
Heat a large saute pan or wok over medium-high heat. Add 2 tablespoons vegetable oil, once hot, add the chicken in a single layer in the pan. Cook without moving for 2 minutes, and then stir and cook for an additional 2 minutes.
Add garlic and ginger, stir-fry until fragrant, 30 seconds. Add the sauce to the pan and allow it to simmer and bubble, 1 to 2 minutes. Mix the cornstarch slurry and then gradually add it to the pan, constantly stirring to combine. Cook until the sauce thickens, 1 minute. Season with more salt and pepper as needed.
Garnish with sliced green onions and sesame seeds. Serve with your choice of sides like rice and vegetables.
For a thicker sauce: Add 1 tablespoon of cornstarch mixed with 2 tablespoons cold water.
Make it Whole30 or Paleo diet: Substitute 1 tablespoon arrowroot powder for 2 teaspoons cornstarch.