In a large stockpot, sauté the onion, celery, and carrot in a tablespoon or so of olive oil—just enough to cover the bottom of your pot—over low heat. Meanwhile, peel and quarter the sweet potato. When the onion has softened, after about 8 minutes, add the sweet potato to the pot along with 6 cups of water, the cloves, and a little salt and pepper. Bring to a boil, then lower the heat and simmer until the sweet potato is completely soft, about 30 minutes.
Fish out the cloves, then puree the mixture in a blender or food processor, or if you’re working without fancy tools, by mashing the sweet potato into the side of the pot with a wooden spoon and stirring. If not using immediately, let cool, then cover and refrigerate for up to 5 days or freeze for up to 2 months.