Mix the sauce first. In a small bowl, whisk together the soy sauce, water, honey, brown sugar, rice vinegar, black pepper, and red pepper flakes if you want a little heat.

Make the cornstarch slurry. In another small bowl, stir the cornstarch with the cold water until smooth. Set it aside so it is ready when you need it.

Cook the broccoli. Heat the olive oil in a large skillet or wok over medium-high heat. Add the broccoli and cook for about 3 to 4 minutes, stirring often, until it turns bright green and starts to soften.

Add a splash of water if needed. If the broccoli is browning too quickly, add 2 to 3 tablespoons of water and cover the pan for 1 minute. This helps steam it without making it mushy.

Cook the chicken. Push the broccoli to the side of the pan or remove it temporarily. Add the sesame oil, then the ground chicken. Break it apart with a spoon and cook for 5 to 7 minutes until it is no longer pink.

Add the garlic and ginger. Stir them into the chicken and cook for 30 seconds, just until fragrant. This step builds the base flavor of the stir fry.

Pour in the sauce. Add the teriyaki sauce mixture to the pan and stir everything together. Let it simmer for 1 to 2 minutes so the flavors start to blend.

Thicken the sauce. Stir the cornstarch slurry again, then pour it into the pan. Cook for another 1 to 2 minutes until the sauce looks glossy and slightly thickened.

Finish and serve. Taste and adjust the seasoning if needed. Spoon the stir fry over rice and top with sesame seeds and green onions.