Bring a large pot of lightly salted water to a boil. Add the noodles and boil for about 6 minutes, or according to the package instructions, until soft.
Meanwhile, make up the lemon juice to 1⁄2 cup with water, if necessary, then blend with the cornstarch in a bowl or jug until smooth. Stir in the stock, soy sauce and sugar, then add the lemon zest and chili pepper flakes. Set aside.
Heat a wok or large frying pan over a high heat. Add the cashews and stir for about 1 minute until browned in places. Tip them out and set aside.
Return the wok to the heat and add the oil, swirling it around to coat the sides. Add the onions and garlic and stir-fry for 3 minutes or until tender. Add the chicken pieces and stir-fry for 2-3 minutes until the chicken is cooked through and beginning to brown.
Pour in the reserved lemon-flavoured sauce and add the broccoli florets and ginger. Bring to a boil, then cover and simmer for 4-5 minutes until the broccoli florets are tender but still crisp.
Drain the noodles well, then add them to the wok. Use two large forks to mix them in with the other ingredients. Scatter the cilantro and cashews over the top, then serve.
Each serving: 38.5 g protein, 30 g fat of which 5.5 g saturates, 53 g carbohydrates 6 g fibre, 649 Calories