Peel potatoes; cut into 1-inch pieces.
Bring potatoes and cold water to cover to a boil in a large saucepan, and boil 12 minutes or until tender.
Drain and return potatoes to pan. Add sour cream and next 4 ingredients. Mash with a potato masher or fork until smooth. Garnish, if desired. Serve warm.
Note: To make ahead, place prepared Southwest Mashed Sweet Potatoes in a lightly greased 11- x 7-inch baking dish; cover and chill up to 2 days. When ready to serve, let stand at room temperature 45 minutes; top with 1 tablespoon cut up butter, and bake, uncovered, at 350° for 35 minutes or until thoroughly heated.