1. In a medium saucepan over high heat, bring sweet potatoes and broth to a boil. Reduce heat to medium-low and simmer uncovered for 20 minutes, or until sweet potatoes are very soft.
2. Remove from heat. Using an immersion blender, puree in pan until smooth. (Alternatively, puree in a regular blender.)
3. Stir soy milk into soup over medium-high heat. Bring just to a boil.
4. Serve soup hot in espresso cups or large shot glasses, topped with 1 tablespoon whipped cream.