Regardless of method, once you have cooked your sweet potatoes, let them cool for a few minutes, and then scoop out the flesh. You have 2 options to mash them: By hand: Put the sweet potato flesh into a medium mixing bowl and mash with a fork or potato masher until pureed. A few small chunks are fine. Food processor or blender: For a perfectly smooth filling, puree the sweet potatoes and butter in a food processor or blender.