Finely chop the stalks of the green onion, separating the white bits from the green bits.
Add a dash of oil to a large saucepan over high heat. Add the brown onion and saute for 5-10 minutes or until it is translucent. Add the white parts of the spring onion, garlic and ginger and saute until everything is fragrant and has softened.
Add the miso paste, tahini, soy sauce, vinegar, chilli flakes and a dash of stock to the saucepan. Saute until everything is caramelised. Add the remaining vegetable stock, boil for 5 minutes then reduce to medium heat. Let the broth simmer for at least 20 minutes to let the flavours develop.
If you would like a thick stock, carefully pour the stock into a blender and blend until everything is smooth. If you would like a thin stock, leave the chopped ingredients in the soup or pour the soup through a sieve discarding the solids. Return the stock to the saucepan.
While your stock is simmering, cook the noodles according to its packet instructions.
Add oil to a large fry pan. Lightly fry the tofu on both sides until golden. Set aside.
10 minutes before eating, add the bok choy to the noodle soup to cook.
To serve, divide the soup, boy choy, noodles, tofu and carrots into 4 bowls. Enjoy immediately. All components can be stored in an airtight container in the fridge for up to 5 days. Alternatively, the soup can be frozen in an airtight container for up to 1 month.