In the bowl of a stand mixer fitted with the paddle attachment combine flour, baking powder, confectioners' sugar, ground hazelnuts, cinnamon, and salt. Add maple syrup and cubed cold butter.
Mix on medium speed for about 1-2 minutes until you have a smooth dough. Wrap the dough in plastic foil and let it rest in the refrigerator overnight.
Preheat the oven to 350°F (177°C) and line two large baking sheets with silicone mats or parchment paper.
Remove dough from the refrigerator and divide it into eight pieces. On a lightly floured work surface roll each one into a 1/2-inch thick log. Slice each log into 2-inch long logs and place log cookies on baking sheets about 2 inches apart. Don't let the dough get too warm!
Bake the cookies for 11-12 minutes or until lightly brown around the edges. Allow to cool for 5 minutes on the baking sheet, then transfer to cooling rack to cool completely.
Melt the chopped dark chocolate in a double boiler or use the microwave. For the microwave, place the chocolate in a medium heat-proof bowl. Melt in 15-second increments, stirring after each increment until completely melted and smooth.
Dip each completely cooled cookie 1/4 into the chocolate from both sides and place onto a baking sheet lined with a silicone baking mat. Top with sprinkles. To help the chocolate set you can place the baking sheet into the refrigerator.