Using a stand mixer or electric mixer, cream the butter and sugar together until smooth and creamy
Beat in egg and vanilla, until smooth
Add flour, cornstarch, baking soda and salt, and stir until just combined.
Fold in chocolate chips and Andes Mint Thins
Cover and refrigerate for minimum 2 hours or overnight
Preheat oven to 350°F and line a cookie sheet with parchment paper
Using a cookie scoop or tablespoon, scoop dough onto parchment paper lined cookie sheets, about 1½ inches apart
Bake in preheated oven for 12-14 minutes, cookies will still look a little wet in the center
Allow to cool 2 minutes on the cookie sheet before transferring to a wire rack to finish cooling
Store in an airtight container at room temperature for up to 5 days
