Cook bacon in a Dutch oven over medium heat until crisp. Remove bacon from pan, reserving drippings in pan. Crumble bacon; set aside. Ad leek and onion to pan; saute 4 minutes. Add broth, potato, lentils, carrot, and salt; bring to a boil. Cover, reduce heat and simmer 1 hour or until vegetables are tender. Place vegetable mixture in blender or food processor; process until smooth. Return pureed mixture to pan; stir in half and half and sherry. Cook until thoroughly heated. Sprinkle with bacon.