In a small bowl, whisk together the soy sauce, cold water, cornstarch, honey, garlic, and ginger. Set aside.
Pat the chicken dry with paper towels. Place the chicken in a medium bowl and season with salt and pepper to taste. Add the cornstarch and toss to coat.
Heat the vegetable oil in a large skillet over medium-high heat. Working in batches, cook the chicken in the hot pan until it’s nicely browned, about 5-6 minutes. Do not cook too many chicken pieces at once, since they need plenty of space in the pan to spread out and brown. Add extra oil to the skillet for each batch, as needed. Remove the chicken to a plate or bowl and tent with foil to keep warm while you simmer the sauce.
Reduce the heat to medium. Whisk the sauce again to make sure that all the ingredients are completely combined. Pour the sauce into the skillet and cook, whisking constantly, until the sauce thickens, about 1 minute. Remove from the heat. If the sauce gets too thick, just add extra water about ¼ cup at a time, to thin to desired consistency.
Stir the chicken into the sauce. Taste and season with additional salt and pepper, if necessary. Garnish with green onions, red pepper flakes, and toasted sesame seeds if desired.
