1Spray 3-quart saucepan with cooking spray; heat over medium heat. Add leek; cook and stir about 3 minutes or until softened. Increase heat to high. Add broth and baking potatoes. Heat to boiling; reduce heat. Cover; gently simmer 5 minutes.
2Add sweet potatoes. Cover; gently simmer about 10 minutes or until potatoes are tender when pierced with fork.
3Using slotted spoon, remove baking potatoes from saucepan; place in blender. With lid on saucepan, carefully drain off broth into blender, leaving leek and sweet potatoes in saucepan. Cover blender; puree potato mixture until smooth. Return mixture to saucepan.
4Stir in remaining ingredients. Cook over medium heat about 8 minutes, stirring occasionally, until thoroughly heated.