Heat the oil in a wok or a large saute pan over high heat. Dust the chicken with cornflour. When the oil is hot, add the chicken, and cook until it just turns opaque, about 3 to 4 minutes. Add the green onion bottoms, garlic, and crushed red pepper and cook until fragrant, about 30 seconds. Add the mange tout, red pepper, onion, celery, and cook until just tender, about 1 minute.
Add the chicken stock, hoisin, and soy sauce to the wok. Stir to combine. Move the contents of the wok to the side to reveal a well. Submerge the cellophane noodles into the liquid. Cover the noodles with the chicken and vegetables and cook 1 minute longer.
Remove the chicken from the heat. Add the spring onion tops, roasted cashews, and toss to combine all the ingredients. Season the mixture with salt, and pepper, to taste, and serve immediately.