Boil the water and pour over the miso in a glass measuring jug or a mug. Stir well until dissolved/mixed in.
Heat up a large saucepan on medium heat. Add the coconut oil and the garlic, stirring for a minute until fragrant. Add in the miso mixture, stock, salt, pepper and shiitake mushrooms. If using tofu, add this now.
Increase the heat to high and cook for 5 minutes to allow the liquid to reduce and the mushrooms to cook. At the same time, cook the noodles according to the packet instructions.
When ready to serve, add noodles to the bowl along with protein (if not using tofu) followed by the soup. Garnish with the red cabbage and torn nori sheets.