1. Preheat the oven to 350°F and line 2 baking sheets with parchment paper.

2. In a medium bowl, whisk together the flour, cocoa powder, baking soda, and salt.

3. In a large bowl, beat the softened butter, brown sugar, and granulated sugar until light and creamy.

4. Add the eggs one at a time, then mix in the vanilla extract and peppermint extract.

5. Gradually add the dry ingredients to the wet mixture and mix until just combined.

6. Fold in the chocolate chips and most of the crushed peppermint candies.

7. Scoop the dough into 2-tablespoon portions and place them on the prepared baking sheets, spacing them about 2 inches apart.

8. Press a few extra chocolate chips, crushed peppermint pieces, and optional sanding sugar onto the tops.

9. Bake for 9 to 11 minutes, until the edges are set and the centers are still slightly soft.

10. Cool on the baking sheet for 5 minutes, then transfer to a wire rack to cool completely.