Saute the onion, carrot and celery in the olive oil. Add garlic and saute until the onion is translucent.
Transfer the saute into a food processor with 1 cup of vegetable broth, blend until smooth.
Return to soup pot and add in 2 cups of sweet potato puree and the remaining 3 cups of vegetable broth. Add in spices. Bring soup to a boil, then simmer uncovered for about 15 minutes. Serve immediately.