Combine chicken cubes with cornstarch, water, 1 tablespoon oil, and oyster sauce. Mix until the liquid is absorbed. Marinate for 15 minutes.

Mix the sauce: whisk together chicken stock, honey, light soy sauce, hoisin sauce, dark soy sauce, rice wine vinegar, sesame oil, and white pepper. Set aside.

Heat 2 tablespoons oil in a wok over high heat until smoking. Spread chicken in a single layer and fry for 1 minute per side until golden. Transfer to a bowl.

Add remaining 1 tablespoon oil. Stir-fry ginger for 5 seconds, then add garlic. Immediately add red bell pepper, scallions, and water chestnuts. Stir-fry for 1-2 minutes.

Return chicken to the wok. Pour in the sauce and toss over high heat until the sauce thickens and glazes everything, about 1 minute.

Add roasted cashews and toss to combine. Serve immediately over steamed rice.