Tender and moist, these muffins are lightly sweetened with warm spices. Plan to prepare the sweet potatoes at least an hour—and up to 3 days—before you start making the muffins to allow time to cool. You can make these plain, with chocolate chips, or with lemon zest.
Preheat the oven to 375 degrees F and grease a standard-size 12-cup nonstick muffin tin well. (I use classic Pam spray.)
Add the sweet potato, milk, butter, maple syrup, egg, and vanilla to a medium bowl. Stir together, going slowly and gently, until fully combined.
In a separate medium bow, stir together the flours, baking soda, cinnamon, and salt. Add the optional sugar if using. Stir gently into the sweet potato mixture.
To add chocolate chips, sprinkle a few on top of each muffin before baking or stir into the batter. To add lemon zest (without chocolate), stir the fresh lemon zest into the batter.
Divide among the prepared muffin tin, using about 1/4 cup batter in each, and bake for 16-20 minutes or until a cake tester inserted into the center of a muffin comes out clean. (In my oven it was right at 18 minutes. To make as mini muffins, bake for about 12-14 minutes.) Let cool for a minute in the pan, then transfer to a wire rack to cool.
Serve slightly warm or at room temperature.
Store leftovers in an airtight container at room temperature for up to 3 days, in the fridge for up to 5, or in the freezer in a zip-top freezer bag with as much air removed as possible for up to 6 months. Thaw overnight in the fridge or at room temperature.
To make the mashed sweet potato, you can make Mashed Roasted Sweet Potato or Crock-Pot Sweet Potatoes. Do this step ahead of time (even up to three days ahead if you store it in an airtight container in the fridge) so the sweet potato is cool when you make the muffin batter.
These are very lightly sweet. The additional sugar is there if you think your family would prefer them a little sweeter.
Be sure to puree the sweet potatoes fully before starting the batter. I usually run it through my blender to make sure it's smooth and lump-free. You can also use store-bought sweet potato puree.