• Preheat oven to 350℉. Line two 12-cup or one 24-cup muffin pans with cupcake liners.

Make the cupcakes

• Add the cake flour, cocoa powder, baking soda and salt to a small bowl. Mix well and set aside.
• Add the butter and sugar to the mixing bowl. Mix on low until fully incorporated.
• Add the eggs, one at a time, to the mixing bowl. Mix on low until incorporated.
• Alternate adding half of the flour mix and half of the buttermilk. Mix on low until incorporated.
• Chop ½ cup of Thin Mint cookies (approximately 6). Add chopped cookies and peppermint extract to the mixing bowl and mix or stir just until the cookies are evenly distributed.
• Use a large 4 tablespoon cookie scoop to fill each muffin tin.
• Bake for 18-19 minutes, or until a toothpick comes out clean. [If you are using two 12 cup muffin pans on different oven racks, rotate pans halfway through.]
• Cool in the muffin tins for 10 minutes and then move the cupcakes to a wire rack to finish cooling. Allow cupcakes to cool completely before frosting.

Making the Frosting

• Add the butter to a mixing bowl and mix on medium speed until creamy, about 2 minutes.
• Add the powdered sugar, peppermint extract and 2 tablespoons of heavy whipping cream to the mixing bowl. Mix on medium high until light and fluffy, scraping down the sides several times, about 7-8 minutes. [Depending on the temperature of the butter and the humidity of the kitchen, you may need to add 1-2 more tablespoons of heavy cream if the frosting is too heavy/thick. Add the additional tablespoon(s) of heavy cream one at a time.]
• Add the frosting to the cupcakes by using an icing (offset) spatula, a regular knife or by piping it on.
• Lightly press one cookie into the frosting of each cupcake.
• Serve or place in an airtight container.