Cut chicken into 1-inch cubes. Toss chicken in batches with cornstarch, tapping off the excess. Set dredged chicken on a platter and set aside.

In a separate dish, combine all the ingredients for your sauce and whisk to combine.

Preheat a non-stick skillet with oil. Cook chicken in 2 to 3 batches, sautéing until golden on both sides and cooked through then remove the chicken from the pan and transfer to a bowl. Repeat with the remaining chicken, adding more oil as needed. Leave at least 1 tbsp oil in the pan.

Add the garlic, ginger, and pepper flakes. Sauté for about 30 seconds or until fragrant.

Add the sauce to the skillet and bring it to a simmer while stirring. Let it simmer for 1 minute to cook off the vinegar a little. Taste the sauce and add more soy sauce or rice vinegar to taste if desired. Add the chicken and toss to coat. Serve garnished with sesame seeds if desired.