• 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.

Frosting

• In a stand mixer, whip your butter chunks and brown sugar on medium-low speed until the butter is light and fluffy and the brown sugar is incorporated. Then add in the powdered sugar 1 cup at a time and the heavy cream one tablespoon at a time, letting it mix into the butter thoroughly.
  1 cup unsalted butter, 1 cup brown sugar, 5 cups powdered sugar, 5 tbs heavy cream
• Add in the vanilla and a pinch of salt, allowing the ingredients to incorporate fully on medium low speed.
  1 tbs vanilla, Pinch salt