Preheat oven to 350 degrees. Line a cupcake pan with 12 cupcake liners and set aside.
Add the softened butter and granulated sugar to a large bowl. Cream together with an electric mixer until fluffy, 1-2 minutes.
Then add in the egg whites, vanilla and peppermint extract. Mix until smooth and pale in color, about 1 minute.
In a small bowl sift together the cake flour, baking powder, baking soda, and salt.
Alternate adding the buttermilk and the dry ingredients to the butter/sugar/egg mixture. Mix until everything is combined.
Divide the batter evenly between the 12 cupcake liners. Each should be about ¾ way full.
Bake the cupcakes for 17-19 minutes or until a toothpick comes out clean from the centers. Let the cupcakes cool in the pan for 5 minutes then transfer to a cooling rack to cool completely.