Soak dried shiitake mushrooms in water for 30-45 minutes. Skip this step if not using dried mushrooms.
Slice mushroom, tofu and bamboo shoots. Mince garlic.
Bring vegetable broth to a pot and add corn starch to broth. Important: do not heat up pot yet. Corn starch will clump up and is harder to dissolve if broth is hot/boiling. Using a spoon, mix corn starch into broth. Then turn on the heat.
Add garlic, rice vinegar, soy sauce, sesame oil, rice wine, ginger powder, sugar, salt, white pepper and red pepper flakes to broth. Bring to boil.
Once broth is boiled, add sliced mushroom, tofu and bamboo shoots to broth. Bring to boil again. Once boiled, lower heat to medium low and let it simmer for 5-7 minutes.
Taste soup and add more salt if need. Salt will open up the flavors in addition to increasing the saltiness of the broth.
Right before removing soup from heat. Beat an egg in a small bowl and slowly pour beaten egg into soup. Stir while pouring the egg into soup.
Remove from heat. Garnish with green onions. Serve and enjoy!