Preheat oven to 400 degrees.
Add butterkin squash to a baking sheet and toss with 2 Tbsp sunflower or coconut oil and a bit of sea salt. Roast for 12-15 minutes or until tender and cooked through. Set aside to cool slightly.
In the meantime, add coconut milk, vegetable broth, ginger, lemongrass, and onion to a medium sauce pan and bring to a boil. Then lower heat to a simmer.
Add fish sauce (optional) and sliced pepper and stir.
Add butterkin squash to a food processor or blender with 1 cup of the broth and puree until smooth. Add the blended mixture back into the soup and stir until well combined. Add mushrooms and cook for 5-10 minutes more.
Taste and adjust seasonings as needed. Before serving, discard lemongrass. Garnish with fresh lime juice (HIGHLY recommended).
This is tasty over rice or on its own. Store leftovers in covered in the fridge for several days. You can also freeze this soup for longer term storage.