Preheat oven to 400°F. Line two baking sheets with parchment paper.
Beat butter, brown sugar, and granulated sugar in a large mixer on medium-high speed for 3-4 minutes until creamy and light.
1 cup salted butter,, 1 cup light brown sugar, 1/2 cup granulated sugar
Add eggs and vanilla. Beat again until combined, scraping the bottom and sides of the bowl.
2 large eggs, 2 teaspoons vanilla extract
Add flour, cornstarch, baking soda, and salt. Mix just until combined.
3 cups all-purpose flour, 2 teaspoons cornstarch, 1 teaspoon baking soda, 3/4 teaspoon salt
Stir in Andes peppermint baking bits, chopped Oreos, and chocolate chips.
1 (10-ounce) bag Andes peppermint crunch pieces, 1 1/2 cups roughly crushed Oreo cookies, 1/2 cup semisweet chocolate chips
Use a large 1/4 cup cookie scoop to scoop balls of dough onto the prepared baking sheet, spacing them a couple inches apart so they have room to spread.
Bake for 10-12 minutes until set and just golden brown around the edges but still soft and slightly underbaked in the middle. Cool for at least 5 minutes on the cookie sheets before transferring to a wire rack to cool completely.