Lightly fry onion in the oil. Add garlic and finely minced ginger and fry another minute.
Add broccoli, courgette and stir fry 4-5 mins. Add mushrooms and fry another minute. Add water (about 2 cups). Stir.
Then add tamari. Bring to a gentle boil. Add udon noodles and let simmer a few minutes to cook the noodles. Add spinach leaves and let cook a further minute until the leaves are just wilted.
Remove from heat. Stir through the miso until it is dissolved.
Serve immediately, garnished with chopped fresh coriander.