Add the sweet potatoes and water to a saucepan. Bring the water to a boil, then reduce the heat to a simmer. Cover and cook for 10 minutes or until the sweet potatoes are soft. Allow this to cool.
Pour the contents of the saucepan into a blender along with the remaining ingredients and blend until smooth.
Add the sauce back to the saucepan over medium heat and stir for 3-4 minutes until hot.
If you want a thinner consistency, add water to the pan and stir.
Serve warm.
Notes
If you prefer a thinner consistency you can add more hot water to the sauce.