Preheat the oven to 350 degrees and line 10-12 muffin tins with patty pans and set aside. In a large mixing bowl, combine the dry ingredients and mix well. In a small bowl, whisk the milk, vanilla extract and egg/flax egg. Pour into the dry mixture, along with the mashed sweet potato. Add the melted nut butter and mix very well until a batter is formed. Using a 1/4 cup, pour batter into the patty pans/muffin liners/muffin tin until almost full. Top with extra cinnamon and bake for 25-30 minutes, or until a toothpick or skewer comes out clean. Remove from oven and allow to sit for 5 minutes, before removing and allowing to cool on a dry surface.