Preheat your oven to 350°F (175°C). Line two large baking sheets with parchment paper or silicone baking mats to prevent the cookies from sticking and ensure even baking.
In a large mixing bowl, beat the softened butter, granulated sugar, and brown sugar together until the mixture is light and fluffy. This usually takes about 2 to 3 minutes using an electric mixer.
Add the eggs one at a time, beating well after each addition. Mix in the vanilla extract and the peppermint extract until fully combined and the batter is smooth.
In a separate bowl, whisk together the flour, cocoa powder, baking soda, and salt. Gradually add the dry ingredients to the wet mixture, mixing on low speed until just combined. Be careful not to overmix the dough.
Using a spatula, gently fold in the chocolate chips and about half of the crushed peppermint candies. This ensures every bite has a bit of crunch and extra chocolatey goodness.
Scoop rounded tablespoons of dough and place them 2 inches apart on the prepared baking sheets. Bake for 9 to 11 minutes, or until the edges are set but the centers still look slightly soft.
Immediately after removing the cookies from the oven, sprinkle the remaining crushed peppermint candies over the top. Let the cookies cool on the baking sheet for 5 minutes before transferring them to a wire rack to cool completely.