In a large pot, heat the oil. When hot, add the leeks and sauté on medium high heat until leeks are lightly browned, 8-10 minutes. When cooked, pour in coconut milk, stock, carrots, and celery. Bring liquids to a simmer, and then add in the spices and lime leaf. Salt and pepper lightly, then cover with lid and allow to simmer on medium low for 10 minutes.
Next, add in butternut squash and continue to simmer for 22 minutes or so. The carrots and celery should be very soft. Taste broth occasionally and add salt and pepper accordingly.
When all ingredients are tender, transfer to a heat safe blender, and blend until smooth. Taste if any additional salt is needed.