In a small bowl, whisk together the soy sauce, brown sugar, rice vinegar, ginger, and garlic to create the teriyaki sauce base.
Heat the vegetable oil in a large skillet or wok over medium-high heat.
Add the bite-sized chicken pieces to the skillet and cook for 5 to 7 minutes, stirring occasionally, until browned on all sides and cooked through.
Pour the teriyaki sauce mixture over the chicken in the skillet. Reduce the heat to medium and let it simmer for 2 minutes.
Stir the cornstarch and water slurry, then pour it into the skillet. Stir constantly for 1 to 2 minutes until the sauce becomes thick, glossy, and sticks to the chicken.
Divide the warm cooked white rice and steamed broccoli florets evenly between two bowls.
Top each bowl with a generous portion of the sticky teriyaki chicken and its glaze.
Garnish with sesame seeds and sliced green onions before serving hot.