Season the salmon: Lightly season the salmon with salt and pepper.
Mix the Miso Seasoning Base: In a small bowl, mix together the miso paste, soy sauce, mirin, and sake until smooth.
Assemble the pot: In a medium pot, add the napa cabbage and mushrooms. Drizzle the seasoning base over the vegetables, then place the salmon on top. Pour in the stock around the sides of the pot. The salmon does not need to be fully covered, just ¼ is good. As the stew cooks, the napa cabbage and mushrooms will release moisture and soften down, gently cooking the salmon so it stays tender and delicate.
Cook: Cover the pot and bring to a gentle simmer over medium heat. Once simmering, cook for 8 minutes, or until the salmon is cooked through.
Serve: Garnish with green onion and serve warm.
