Place the stock, cornstarch, soy sauce, honey and chili sauce, if using, in a small bowl, mix to combine, and then set aside.
Place the oil in a large nonstick skillet or wok set over medium-high heat. When hot, add garlic, ginger, onion, carrot, celery, bell pepper and mushrooms and stir-fry 3 to 4 minutes, until crisp/tender. Add the cornstarch mixture and bring to a simmer. Toss in the bean sprouts, green onion and cashews, heat through a few seconds, and then serve.