In a small frypan, heat 2 teaspoons of sesame oil. Once the oil has heated up, add the finely chopped ginger, lemongrass, and chilli and sauté together until soft. Once softened, add a couple of splashes of soy sauce.
In a large saucepan, boil 5-6 cups of water (depending on how many people you’re feeding!) Add the mixture from your fry pan to the boiling water and simmer for 5 minutes.
Add the roughly chopped wedges of mushroom, baby sweetcorn and tofu to the simmering mixture. At the same time, add your udon noodles to a saucepan of water at a rolling boil and cook according to packet instructions.
In the last 2 minutes, add 2 tablespoons of miso paste and the bok choy to the soup mixture. Once the udon noodles have cooked, add those to the soup mixture as well.