In a large pot, heat the oil. When hot, add in the leeks, and sauté on medium-high heat until leeks are lightly browned, about 8-10 minutes. When cooked, pour in coconut milk, stock, carrots, and celery. Bring liquids to a simmer and 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.