Preheat oven to 350 degrees. Spray a baking sheet with non-stick cooking spray or line with parchment paper if not using a non-stick baking sheet.
In a medium bowl, whisk together the flour, cocoa powder, baking powder, baking soda, and salt. Set aside.
2 ½ cups all purpose flour, ½ cup Dutch processed cocoa powder, ½ teaspoon baking powder, ½ teaspoon baking soda, ½ teaspoon kosher salt
In a large bowl, using an electric hand mixer or in the bowl of a stand mixer fitted with paddle attachment, cream the butter, sugar, and brown sugar until light and fluffy.
½ cup unsalted butter, 1 cup granulated sugar, ¼ cup light brown sugar
Mix in the eggs. Add the sour cream, vanilla extract, and peppermint extract; mix until well combined.
2 large eggs, ¾ cup sour cream, 1 teaspoon vanilla extract, ¾ teaspoon peppermint extract
Slowly add in the flour mixture and continue mixing just until everything is combined.
Using a medium sized cookie scoop (2 tablespoons in volume), drop balls of cookie dough onto the prepared baking sheet. Lightly spray your hand or the back of a glass with cooking spray and flatten the cookies to half the size. (The dough is wet which is why I mentioned to spray whatever you are flattening the dough with). Bake for 8-10 minutes, until the tops no longer look wet.
Allow to cool for a minute or two on the cookie sheet and then transfer to a cooling wire rack. Allow to cool completely before frosting.