Bring a small pan of water to the boil and gently lower the egg in. Set a timer for 6 minutes.
Meanwhile, heat the groundnut oil in a wok over a medium to high heat, add the mushrooms and stir-fry for 2 minutes. Add the ginger, garlic, chilli flakes, spring onions and beansprouts and stir-fry for another minute. Add the miso, soy and the cooked noodles. Mix well to combine then cook for a further minute.
When the 6 minutes is up on the egg, pour the hot water away, add cold water to the pan and peel the egg gently when cool enough to touch.
Season the noodles to taste and serve in a shallow bowl. Top with the egg halved and a sprinkling of chilli flakes.