Prepare the ingredients: Clean the sweet potatoes by cutting off the tips and peeling the skin. Cut the sweet potatoes into one-inch cubes, and then rinse them in running water.
Boil the sweet potatoes: Add water to a large pot and bring to a boil. Then, add the sweet potatoes and boil for 15 minutes, or until they are tender and fully cooked.
Blend the sweet potatoes: Use a handheld immersion blender and blend the sweet potatoes. When they are pureed, add three tablespoons of butter and continue mixing until everything is well combined.