Preheat your oven to 350°F (175°C) and line a baking sheet with parchment paper.
In a large bowl, beat the softened butter, granulated sugar, and brown sugar together until light and fluffy.
Mix in the eggs, one at a time, then add the vanilla and peppermint extracts, blending well.
In a separate bowl, whisk together the flour, cocoa powder, baking soda, and salt.
Gradually add the dry ingredients to the wet mixture, stirring until just combined. Fold in the chocolate chips and crushed peppermint candies.
Using a tablespoon or a cookie scoop, drop rounded balls of dough onto the prepared baking sheet, spacing them about 2 inches apart.
Bake in the preheated oven for 10-12 minutes, or until the edges are set but the centres are still slightly soft.
Allow the cookies to cool on the baking sheet for a few minutes before transferring them to a wire rack to cool completely.