1. Preheat your oven to 375 F (190 C). Line two baking sheets with parchment paper or silicone baking mats.

2. In a large mixing bowl, using an electric mixer, cream together the softened butter and granulated sugar until the mixture is light and fluffy. This usually takes about 2-3 minutes.

3. Beat in the eggs one at a time, mixing well after each addition. Then, stir in the vanilla extract and peppermint extract until fully combined.

4. In a separate medium bowl, whisk together the all-purpose flour, unsweetened cocoa powder, baking soda, and salt. Make sure there are no lumps of cocoa powder.

5. Gradually add the dry ingredient mixture to the wet ingredients, mixing on low speed until just combined. Be careful not to overmix; stop as soon as no streaks of flour are visible.

6. Gently fold in the semi-sweet chocolate chips and crushed peppermint candies using a spatula. Distribute them evenly throughout the dough.

7. Drop rounded tablespoons of dough onto the prepared baking sheets, leaving about 2 inches between each cookie. Bake for 10-12 minutes, or until the edges are set and the centers still look slightly soft.

8. Remove the baking sheets from the oven and let the cookies cool on the sheets for 5 minutes before transferring them to a wire rack to cool completely.