Wash all vegetables. Separate white and green parts of the scallion; reserve the green parts for garnishing.
To make the broth: Boil together white parts of the scallion, ginger, garlic, dry shiitake mushrooms, soy sauce, nutritional yeast and water. Let it simmer for 10 minutes. Strain the mixture and discard solids. Adjust the seasoning and bring it to a boil again.
While simmering the broth, heat up the olive oil in a frying pan. Season the sliced tofu with soy sauce and sauté both sides of the tofu until browned. Set aside.
Once the broth starts boiling, cook the soba noodles in the broth for 3-4 minutes or according to the instructions on packet. About 1 minute before the soba is fully cooked, add in baby bok choy, snow peas and shiitake mushroom.
Pour noodles into individual bowls and garnish with cooked tofu, red chilies and chopped scallions. Drizzle with sesame oil. Serve hot.