Cookies. In a medium bowl, combine flour, cocoa powder, baking powder, and salt. Mix well and set aside.
In a large mixing bowl, whisk together sugar and butter for 30 seconds, or until combined.
Add egg and peppermint extract, and whisk until smooth. Gradually add the dry ingredients. Mix gently with a wooden spoon until combined.
Add dark chocolate chips into the dough. Mix well and refrigerate the dough for 30 minutes - 2 hours.
Preheat the oven to 350F. Line a large baking tin with parchment paper.
Roll the dough into walnut-size balls and arrange them on the sheet, keeping at least 2 inches distance between each dough.
Bake the cookies for 12 minutes, or until the bottoms are well set. Let them cool on a wire rack.
To decorate cookies: use a teaspoon to draw zig-zag lines on top of the cookies with melted chocolate. Then, sprinkle crushed candy cane on top.