In a large Dutch oven over medium heat, combine olive oil and diced onion. Cook, stirring occasionally for 5-7 minutes or until the onion is translucent.
Add garlic and cook for 1 minute longer.
Add squash, vegetable stock, coconut milk and curry paste. Bring to a boil, reduce heat to low and cover. Cook with the lid on for 15 minutes or until the squash is fully cooked through.
Remove from heat and using an immersion blender, puree the soup. (You can also CAREFULLY blend the soup in a blender.)
Add salt and pepper to taste and serve garnished with green onion.