Heat the 2 tablespoons of olive oil over medium-high heat in a large Dutch oven or other big pot. Add 1 chopped onion and 1 1/2 pounds chopped carrots and season with 1 teaspoon salt and 1/2 teaspoon pepper. Cook, stirring occasionally until onions are beginning to brown.
Add the 2 tablespoons of chopped ginger and 1 tablespoon green curry paste and stir until ginger begins to brown. Add the 1 quart of vegetable stock and stir, scraping any browned bits on the bottom of the pan, then add the butternut squash.
Bring soup to a boil, then reduce heat to a slow simmer. Cover and cook, until carrots are very tender, about 20 minutes. Remove from heat then add the can of coconut milk, 2 tablespoons fish sauce and 1 tablespoon lime juice. Stir to combine.
Ladle soup into blender about halfway full. Cover with a clean kitchen towel or rag you don't mind getting dirty and while holding the towel down with one hand, turn blender on low. Slowly increase blender speed until mixture is smooth. Repeat until all soup is pureed. You can also use an immersion blender, if you have one, to puree the soup right in the pot.
Return to pot and bring to a simmer. Taste and add more salt and pepper as needed. Ladle into bowls and sprinkle with chopped cilantro, a few pumpkin seeds and a drizzle of chili oil, if you'd like.