In a medium casserole, heat the oil over a medium heat and add the onion. Allow to soften for about 15 minutes to develop their sweet flavour before adding the garlic and ginger. Sweat for a further 3–4 minutes before adding the spices. Next add the soy bean chilli oil and give this a couple of minutes on the heat, before adding the water. Whisk in the miso paste, followed by the mirin, nutritional yeast, Marmite, soy and sugar. Allow the sauce to reduce on a low simmer for 30 minutes and then add the soy milk. Transfer to a food processor and blitz until smooth, then return to the pan.
Meanwhile in a frying pan heat a glug of oil and fry the mushrooms over a high heat for 5 minutes until they start to caramelise, then set aside. Return the pan to the heat, add a little extra oil if necessary, ramp up the heat and fry the tofu for a minute on each side, or until really charred. Put the teriyaki sauce in a bowl, add the tofu and the eggs and coat thoroughly. Set to one side.
When ready to serve, divide the noodles between two ramen bowls and pour a quarter of the soup base into each bowl. Slice the eggs in half and place on top. Slice the tofu into strips and arrange next to the eggs, followed by the butternut squash and kimchi. Finally, sprinkle the spring onions, chilli powder and sesame seeds over the top and serve immediately.