Place a soup pot over medium-high heat with 2 turns of the pan EVOO, about 2 tablespoons. Once hot, add the kielbasa and cook until brown and crispy, about 4-5 minutes. Remove from the pot and reserve on paper towel-lined plate.
To the same pot, add the leeks, thyme, garlic, hot sauce, nutmeg, salt and freshly ground black pepper. Cook, stirring frequently, for 8-10 minutes, until the leeks are tender.
Transfer leeks to a food processor along with about 2 cups of the chicken stock and pure until smooth. Add the chunks of sweet potato and another 4 cups of the chicken stock — work in batches if you have a small food processor or if you are working with a blender. Pure until smooth and return to the soup pot, adding enough chicken stock to achieve a thick and creamy soup consistency.
Turn the heat on to medium-high, bring up to a bubble and simmer a couple of minutes. Serve the soup topped with some of the crispy turkey kielbasa and a dollop of sour cream, if desired.