Make teriyaki sauce: whisk soy sauce, honey, garlic, sesame oil, and cornstarch together in a small bowl. Set aside.
Dice chicken breast into 1-inch pieces. Pat dry.
Heat olive oil in a large skillet over medium-high heat.
Add chicken and cook without stirring 3 minutes to build a golden crust. Stir and cook 3 more minutes until cooked through.
Reduce heat to medium. Pour teriyaki sauce over chicken. It will bubble and thicken immediately — stir to coat every piece. Cook 1–2 minutes until glossy and caramelized. Don't walk away.
Meanwhile steam broccoli until bright green and tender-crisp, about 4 minutes.
Serve chicken and sauce over rice with broccoli on the side.