Put the chicken, peanut butter, tomatoes, curry powder, and cayenne in a medium pot and pour in the sweet potato broth. Season with salt to taste. Simmer over medium heat until the peanut butter is completely blended and the stew has a thick, even consistency, 20 minutes.
Ladle the stew into bowls and serve, sprinkling the chopped nuts over the top as a garnish.
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.