Preheat the oven to 350 degees. Line two baking sheets with parchmnet paper and set aside.
In a medium bowl, whisk together the flour, cocoa powder, baking powder, baking soda and salt.
1 ¼ cups (156 g) all-purpose flour, spooned and leveled, 6 tablespoon (30 g) Dutch process cocoa powder, ½ teaspoon baking powder, ½ teaspoon baking soda, ½ teaspoon salt
Add softened, unsalted butter, light brown sugar, and granulated sugar to a large bowl. Cream the butter and sugars together with an electric mixer for two minutes, or until light and fluffy. (You can also use a stand mixer with a paddle attachment.)
¾ cup (168 g) unsalted butter, softened, ¾ cup (165 g) light brown sugar, packed, ¼ cup (50 g) granulated white sugar
Add in the egg yolks, peppermint extract and vanilla and mix on medium speed for two minutes, or until the mixture is pale in color and fluffy.
2 egg yoks, at room temperature, ½ teaspoon peppermint extract, 1 teaspoon vanilla extract
Add the dry ingredients to the wet ingredients and mix on low speed just until combined.
Add in the chopped Andes mints and gently fold them into the cookie dough with a rubber spatula.
30 Andes mints, chopped
Scoop the dough into 17 balls using a 2-tablespoon capacity cookie scoop.
Arrange the dough balls two inches apart on the prepared baking sheets. Bake the cookies for 10-12 minutes. (10 for chewier cookies, 12 for crispier cookies.)
Let the cookies cool on the baking sheet for 5 minutes, then transfer them to a wire rack to completely cool. Once each cookie is almost all the way cooled, add an Andes mint on top of the cookie. Then once all the way cooled, sprinkle the top of each cookie with chopped Andes mint pieces, and serve!
17 Andes mints, whole, 2-3 Andes mints, chopped