In the bowl of a stand mixer fitted with the paddle attachment combine flour, baking powder, and sugar. Add vanilla extract, egg yolk, egg, and cubed cold butter. Beat for 1-2 minutes until a smooth dough forms.
Turn the dough out onto a floured work surface and divide into two. Shape each half into a log, about 2 inches in diameter. Tightly wrap the logs in plastic wrap and chill in the refrigerator for at least 4 hours or overnight.
Preheat oven to 350°F (177°C). Line two large baking sheets with parchment paper or silicone baking mats. Set aside.
In the clean bowl of a stand mixer fitted with the whisk attachment beat egg whites at high speed until stiff. Add confectioners' sugar, cinnamon, and almond extract. Whisk until combined. Fold in the ground almonds using a silicone spatula, making sure the ground almonds are evenly moistened.
Remove logs from the refrigerator and slice each log into 0.2 inch thick cookies and place cookies on baking sheets.
Using a small cookie scoop, scoop 1 tbsp of the mixture and place onto each butter cookie slice. You can also use a pastry bag and pipe the mixture onto the cookies.
Bake for about 20 minutes and allow to cool completely on the baking sheets.
Melt the chopped dark chocolate in a double boiler or use the microwave. Drizzle chocolate over cooled cookies and place the baking sheet into the refrigerator to help the chocolate set.