In a large saucepan, bring the vegetable broth to a boil.

Add shiitake mushrooms, bok choy, green onions, garlic, and tofu, and cook for about 10 minutes. The mixture should be at a slow simmer.

Add the udon noodles and cook according to package directions. (Mine needed to cook for about 4 minutes).

Stir in rice vinegar and sesame oil, then season with salt and pepper.

Ladle into bowls and enjoy while the soup is hot.