Heat a large pot or deep skillet over medium heat. Add a small amount of oil, then sauté the onion, garlic, ginger, and white parts of the green onion for about 2 minutes, until fragrant and softened.
1 tsp sesame oil, ⅓ onion, 2 Tbsp garlic, 1" knob ginger, 1 stalk green onion
Add the mushrooms and cook for about 10 minutes, stirring occasionally, until they release their moisture and become tender.
8 oz shiitake mushrooms
Pour in the chicken broth and add the tofu. Allow the broth to heat then bring to a gentle simmer and cook for 3 minutes.
2 cups chicken broth, 16 oz silken tofu
Stir in the remaining seasonings. Cook for another 2 minutes, allowing the flavors to combine.
½ Tbsp chicken bouillon powder, ½ Tbsp soy sauce, ½ Tbsp fish sauce, ½ Tbsp miso paste, ½ tsp salt, ½ tsp pepper
Remove from heat. Carefully transfer the soup to a blender and blend from low to high speed until smooth and creamy. (Blend in batches if needed and allow steam to vent safely in between blending)