Char Onion. Char the onion by either baking in the oven at 400F for 15- 20 minutes or over the stovetop. Scrape off the charred parts. Set aside.
Simmer the broth. In a large stockpot, bring to boil the water (2.5 litres) and add celery, carrots, daikon radish, Chinese cabbage, onion and shiitake mushrooms. Turn the heat down to simmer for 1.5 hours. Once the broth is ready drain the vegetables and set aside.
Cook the toppings. In a large pan heat up oil. Add the mushrooms and fried tofu and stir fry for 3-4 minutes. Add the medium-firm tofu, vegetable stock powder and salt. Gently stir for 2-3 minutes. Avoid stirring to hard otherwise, the tofu will break apart. Set aside.
Prepare noodles. Follow the instructions on the noodle package. For this recipe I used Japanese udon noodles. I bring a pot of water to boil and add the udon noodles. Using chopsticks I loosen the noodles and let it boil for about 1-2 minutes. Drain the noodles and set aside.
Flavor the broth. Add the vegetable stock, salt and sugar to flavor the broth. Add the annatto oil if you are adding to the broth. Turn the heat to medium high and pour the cornstarch slurry. Stir continuously until the soup thickens. Adjust the flavoring to your preference.
Put together your noodle bowl. Add the noodles to the bowl. Top with a variety of vegetarian toppings. Ladle the thickened broth and top with green onions, fried shallots and squeeze some lemon/lime juice. Enjoy!