Preheat Oven: Preheat your oven to 350°F (175°C) and line two baking sheets with parchment paper.
Mix Dry Ingredients: In a small bowl, combine the flour, baking soda, and salt. Set aside.
Cream Butter & Sugars: In a large bowl, use a hand mixer or stand mixer to beat the softened butter, light brown sugar, and granulated sugar together for 1-2 minutes until creamy, scraping down the sides as needed.
Add Wet Ingredients: Add the egg and peppermint extract to the butter-sugar mixture, beating until well combined.
Combine with Dry Ingredients: Gradually add the flour mixture to the wet ingredients, mixing until just combined. Stir in 1 cup of the mint chips, chocolate chips, or Andes candies, reserving the remaining ½ cup for topping.
Shape Cookies: Scoop 2-tablespoon portions of dough and place them a couple of inches apart on the prepared baking sheets.
Bake: Bake the cookies for 9-11 minutes, or until the edges are just starting to turn golden brown while the centers remain slightly underdone. Rotate the baking sheets halfway through the baking time if necessary.
Add Toppings: While the cookies are still warm, press the remaining ½ cup of mint chips or chocolate pieces into the tops of the cookies for a more attractive finish.
Cool: Transfer the baking sheets to wire racks and allow the cookies to cool completely before serving. Enjoy your minty, chocolatey treats!