Preheat your oven to 350°F (175°C) and line two baking sheets with parchment paper.

In a large mixing bowl, cream together the softened unsalted butter, light brown sugar, and granulated sugar for about 2 minutes until light and fluffy.

Add egg yolks, peppermint extract, and vanilla to the mixture, beating on medium speed for 2 minutes until combined and pale.

Gradually sift in the flour, cocoa powder, baking powder, baking soda, and salt, mixing on low speed until just combined.

Fold in the peppermint chips and semi-sweet chocolate chips until evenly distributed.

Scoop the dough into 18 equal balls and place them on the prepared baking sheets, spaced about 2 inches apart.

Bake for 10–12 minutes, removing them at 10 minutes for chewier centers or at 12 minutes for crispier edges.

Let the cookies cool on the sheets for 2 minutes before transferring to a wire rack. Optionally, sprinkle with crushed candy canes.