1. Heat a spoonful of coconut oil in a medium-sized pot over medium heat, add the onions and cook for a few minutes. Add the mushrooms and cook for an additional 2 minutes.
2. Pour in the vegetable broth and coconut milk and bring to the boil. Stir in the miso paste and reduce to a simmer and leave partially covered for 10 minutes. Season to taste with salt if needed.
3. When just ready to serve, heat a skillet over high heat, sear the bok choy by placing it, cut side down on the hot pan until you get some nice browning
4. To serve, ladle broth into two bowls, top with seared bok choy. Sprinkle with sesame seeds.