In a large saucepan, combine the sweet potatoes, water, 3/4 teaspoon salt and cinnamon. Bring to a boil. Reduce heat; simmer, uncovered, for 15-20 minutes or until tender.
Meanwhile, in another large saucepan, cook and stir the pears and onion in butter over medium heat for 5 minutes. Stir in grape juice; bring to a boil. Reduce heat; simmer, uncovered, for 5 minutes. Stir into the sweet potato mixture. Cool slightly.
In a blender, cover and puree soup in batches; return all to one of the pans. Stir in the cream, pepper and remaining salt; heat through (do not boil). Yield: 5 servings.