Preheat oven to 350°F and line a cupcake pan with cupcake liners.
In a small bowl whisk together buttermilk, sweet potato puree, and vanilla
½ cup buttermilk, 1 ½ cups sweet potato puree, 1 teaspoon vanilla
In a separate bowl combine the flour, baking soda, salt, cinnamon, and pumpkin pie spice.
1 ⅓ cups flour, ¾ teaspoon baking soda, ½ teaspoon salt, 2 teaspoon pumpkin pie spice, 1 ½ teaspoon cinnamon
Using a stand mixer, mix sugar and butter until fluffy.
½ cup unsalted butter, 1 ¼ cup white sugar
Once butter and sugar are lighter in color and fully mixed, add each egg and the yolk, one at a time, into the butter mixture, letting each one fully mix into the batter before adding the next. Then add in oil and mix until fully combined.
3 large eggs, 1 large egg yolk, ¼ cup vegetable oil
Fold in ½ of the flour and then fold in ½ of the sweet potato mixture to the batter. Then fold in remaining flour and then remaining buttermilk mixture.
Scoop into lined cupcake tins. Bake for 14 minutes or until a toothpick inserted comes out clean.
Once the cupcakes are done let them cool completely before frosting.
Frost and enjoy!