Note: This cookie dough requires at least 3 hours of chilling. The cookies will be thicker the longer they chill (up to 3 days).
Add the butter, granulated sugar and brown sugar to a large bowl using a hand-held or stand mixer fitted with a paddle attachment. Beat on medium-high speed for 3 minutes, until it's light and fluffy in color. With the mixer still on, beat in the egg and vanilla extract, scraping down the sides of the bowl as needed.
1/2 cup butter, 1/4 cup granulated sugar, 3/4 cup light brown sugar, 1 large egg, 1 teaspoon vanilla extract
In a separate bowl, whisk the flour, cocoa powder, baking soda, and salt together until combined.
1 1/3 cups all-purpose flour, 1/2 cup unsweetened cocoa powder, 1 teaspoon baking soda, 1/2 teaspoon salt
Turn the mixer down to low and slowly add the dry ingredients to the wet ingredients. This helps prevent the flour from flying everywhere.
Add the chopped Andes mints and mix using a rubber spatula to incorporate. Cover the dough tightly with plastic wrap and chill for 3 hours or up to 3 days. Do not skip this step.
1 cup chopped Andes mints
Preheat the oven to 350°F and line two large baking sheets with parchment paper.
Let the dough sit at room temperature for 30 minutes if it's been chilling for longer than a day. Use a large cookie scoop to scoop out the dough. Arrange them on the prepared baking sheet 2-3 inches apart.
Bake the cookies in the preheated oven for 10-12 minutes or until the edges are set and the tops look slightly soft.
Right when they come out of the oven press a whole Andes mint into the top center of the warm cookie. Let them sit to melt then use a toothpick to swirl it around. If the cookies lose their circular shape slightly in the oven you can swirl a wide-mouthed cup around the outside of the cookie to create a perfect circle shape.
18-20 whole Andes mints