Bring a pan of water to the boil, add the stock cube and let it dissolve. Add the noodles and bring back up to the boil.
Add the broccoli and boil for two minutes until the broccoli and noodles are just tender, then drain, rinse with cold water and set aside in the colander.
Cut the chicken into strips, and prepare the mushrooms, onion, pepper, garlic and ginger.
Heat one teaspoon of the vegetable oil in a large non-stick frying pan or wok, then add the chicken. Stir-fry the chicken for two minutes over a high heat until browned.
Take the chicken out of pan, and set aside on a plate while the vegetables are cooked.
Return the pan to the heat and add the remaining oil. Add the peppers, onions and mushrooms. Stir and cook for couple of minutes until just tender, but still brightly coloured, and the mushrooms are just browned.
Add the garlic, ginger and chilli flakes then sizzle for a few seconds till fragrant.
Tip in the drained noodles, broccoli and the chicken and stir-fry until the noodles are hot. Add the hoisin sauce and water mixture, then mix so everything is coated in the sauce. If the noodles seem a bit dry, add a splash more water. To finish, drizzle with the sesame oil, scatter with the roasted nuts and serve immediately.