How to Make It
In a large pot, heat the toasted sesame oil over moderately low heat. Add the onion and sweat for 5 minutes. Add the garlic and ginger and cook for 3 minutes. Add the pumpkin puree, miso, broth and soy sauce, stirring to incorporate, then season with salt and bring to a boil. Reduce the heat to low and simmer for 20 minutes, then remove from the heat and let cool for 10 minutes.
Transfer the soup to a blender (or use an immersion blender in the pot) and puree until smooth. If needed, add additional water or broth to reach the desired consistency. Return the mixture to the saucepan. Serve warm and garnish with nori.