Preheat the oven to 190C/375F. In a medium bowl combine the dry ingredients; flour, cocoa powder, baking soda and salt.
In the bowl of a stand mixer, fitted with a paddle attachment, cream the butter with the brown and white sugar until light and fluffy, then beat in the egg and vanilla.
Add the mixed dry ingredients to the butter and sugar mixture and start combining them on low speed. Stop once in a while, scrape the sides with a flexible spatula and continue beating until the dough forms. Mix in the chocolate chips and give everything a brief mix until the chocolate chips arewell incorporated into the cookie dough but do not overmix.
Scoop the dough with a small cookie scoop and place the dough balls on parchment or silicone lined cookie sheet 1 inch apart as they will spread in the oven. Bake in the preheated oven for 8-10 minutes or until hard around the edges. Take out of the oven and transfer to a wire rack to cool. Repeat the process until all cookie dough is baked.
Chop the candy canes or crush them with a rolling pin. The easiest way to do it is to put them in a ziplock bag, then pound with a rolling pin, so they don't fly everywhere. Melt the chocolate in a double boiler or in a microwave. Watch carefully if using a microwave. I tend to only melt in 40-50 seconds intervals to avoid burning.
Dip half of each cookie into melted chocolate and place it on a cooling rack, then quickly sprinkle that part with crushed candy cane before the chocolate sets. Leave the cookies on the cooling rack until the chocolate hardens.