Prepare the Dough:

1. Mix Dry Ingredients: In a medium bowl, whisk together the flour, cocoa powder, baking soda, and salt. Set aside.
2. Cream Butter and Sugars: In a large bowl, use a hand mixer or stand mixer to cream the softened butter, granulated sugar, and brown sugar until light and fluffy.
3. Add Wet Ingredients: Beat in the egg, vanilla extract, and peppermint extract until fully incorporated.

Combine and Add Mix-Ins:

4. Combine Wet and Dry: Gradually add the dry ingredients to the wet ingredients, mixing just until combined. Avoid overmixing.
5. Fold in Chocolate and Peppermint: Gently fold in the chocolate chips and crushed peppermint candies until evenly distributed.

Bake the Cookies:

6. Preheat Oven: Preheat your oven to 350°F (175°C) and line baking sheets with parchment paper.
7. Form Cookies: Scoop tablespoon-sized portions of dough and roll into balls. Place them on the prepared baking sheets, spacing them about 2 inches apart.
8. Bake: Bake for 12-15 minutes, or until the edges are set but the centers look slightly underbaked.

Cool and Enjoy:

9. Cool on Rack: Allow the cookies to cool on the baking sheet for 5 minutes before transferring them to a wire rack to cool completely.
10. Serve or Store: Once cooled, enjoy immediately or store in an airtight container for later.