- Place the noodles in a large pan of lightly salted boiling water. Return to the boil and simmer for 4 minutes, stirring occasionally with a fork to separate the noodles. Drain, reserving 50ml of the liquid. Rinse the noodles under cold running water. Put aside.
- Meanwhile, whisk together the stock, soy sauce, cornflour and sesame oil in a small bowl until smooth.
- Heat the vegetable oil in a wok or large non-stick frying pan over a medium heat. Reserve some of the dark green parts of the spring onions for garnish, then add the remaining spring onions, garlic, chilli if using, and courgettes to the frying pan. Stir-fry for 3–4 minutes until softened.
- Add the tofu, stock mixture and reserved noodle soaking liquid to the cooking pan. Bring to the boil, stirring constantly for 1–2 minutes or until the sauce thickens.
- Add the noodles and quickly toss together. Remove pan from the heat, toss in the watercress, coriander and reserved spring onions and serve immediately.
*Soba (Japanese buckwheat noodles) would also be good in this dish. Cook for 6 minutes or according to the packet instructions until al dente, then combine in step 5. *If preferred, use peeled, cooked prawns or diced, skinned, cooked chicken or turkey instead of the tofu.