To prepare a sweet potato soup with buttered pecans soups recipe, you will need: Sweet potatoes: Peel and cut the sweet potatoes in half lengthwise. Cut each half into 1/4-inch cubes. Add the cubed potatoes to the crock-pot. Cover and cook on medium-high heat, stirring occasionally, until the potatoes are tender, about 30 minutes. Remove from the heat and stir in the butter, milk, and thyme. Cook, whisking, for 1 to 2 minutes, or until thickened. Serve with sour cream, if desired.