Preheat oven to 400ºF. Wash and prepare sweet potatoes for baking. This recipe takes about 3-5 sweet potatoes. This step can be performed up to 2 days prior to baking muffins. Bake for 45-60 minutes. Allow to cool and then remove peeling from sweet potato and set aside or place in an airtight container in the refrigerator.
Preheat oven to 325ºF. First, cream the melted butter and sugar in a large mixing bowl. Then, combine the eggs and vanilla extract.
Next, combine all-purpose flour, baking soda, baking powder, salt, and cinnamon to the wet mixture (add additional spices if you prefer). Then, combine mashed sweet potatoes.
Prepare a muffin tin and fill each cup with 1/2 cup of the batter. Sprinkle flaxseed onto each muffin.
Bake for approximately 30 minutes. Insert a toothpick into the center of the muffin. Once the toothpick comes out clean, the muffins are done.