Heat oil in a large pot over medium high heat. Add onion and saué until translucent, 3-4 minutes. Add ginger, garlic and mushrooms and continue to sauté until mushrooms are browned. Pour water in and bring to a boil; reduce heat, cover and simmer 30 minutes.
Heat a drizzle of neutral oil in a large pan. Sear bok choy until slightly wilted and browned.
While broth is simmering, bring a small pot of water to a boil and cook noodles for about 30 seconds. Drain and divide between two bowls.
Remove shell from soft boiled eggs and cut in half.
When broth has simmered for 30 minutes, turn off heat, stir in soy sauce and miso. Pour broth over noodles and stir in kimchi liquid, if using. Top with bok choy, soft boiled eggs, sesame seeds, if desired; and serve.