Mix all the sauce ingredients together in a small bowl and keep it aside to infuse while you prepare rest of the meal. Nutritional yeast is added to give it a umami flavor.
Cook noodles according to the package instructions. If using pre cooked ones , they can be added straight to the wok.
Next, if you are using tofu , heat 1 tbsp of oil in a wok or large pan and fry on medium heat until crispy and golden on both sides. Season with salt and pepper.
Take the tofu out in a bowl and keep aside.
In the same wok, add 1 tbsp oil over medium high heat .
Add onions and white part of spring onions and fry until soft. Add chopped ginger and garlic and fry for 1-2 minutes.
Next, add sliced peppers, carrots , cabbage and mushrooms and continue to cook on medium to high heat for 3-4 minutes until vegetables are cooked but firm to the bite. Add pan fried tofu and mix everything nicely. Season with salt and pepper.
Add the noodles. Handle the noodles gently as they are precooked and may break. Next, add the sauce and mix everything gently.
Toss to combine and heat through for 2-3 minutes until udon noodles has absorbed the sauce. Season with more soy sauce or salt if required.
Add chopped green onion and chopped fresh coriander
Serve garnished with green onion, chopped coriander and toasted sesame seeds .