Dice onion and mushroom. I prefer a mix of chunky and finely diced mushrooms and finely diced onion.
In a medium soup pot with lid, sauté onions until translucent in the sesame seed oil. Add diced mushrooms half way through.
Add vegetable stock and bring to a boil. Stir in yellow curry paste and coconut milk, adding more curry paste for a spicier soup. Drain and cut the tofu block into cubes if adding. Slice scallions into thin wafers.
Two minutes before serving, remove two tablespoons of broth and mix with miso paste to temper the miso paste. Add miso mixture and tofu. Let simmer for one minute.
Transfer to bowls and garnish with sliced scallions.