Place a large pot of water over high heat and bring up to a boil to cook the spaghetti. Once boiling, add some salt and the spaghetti and cook until al dente, according to package directions. Drain and toss with a little bit of vegetable oil.
While the water is coming up to a boil to cook the spaghetti, place a large soup pot over medium-high heat and add 2 turns of the pan of vegetable oil, about 2 tablespoons. Add the onion, garlic and shredded carrots and cook until the onions start to get tender, about 4-5 minutes.
Add the mushrooms, zucchini and bok choy and cook for another 2-3 minutes. Add stock, bring up to a bubble then simmer for 5 minutes. Add the bean sprouts the last minute.
In a small bowl, combine the toasted sesame seeds, ground coriander, chili powder and cayenne pepper and reserve for garnishing the soup.
To serve, place some of the spaghetti in a soup bowl and season it with a couple of splashes of tamari. Ladle the veggies and soup over the noodles. Sprinkle the sesame mixture on top and serve.