In a large bowl, combine the flour, cocoa powder, cinnamon, baking powder, and salt. Set aside.

In a separate bowl, beat the butter, brown sugar, and granulated sugar until light and fluffy. Add the eggs, one at a time, and the vanilla. Beat for one minute, until fully combined.

Add the melted chocolate and stir until fully incorporated. Stir in flour mixture until just combined.

Cover the dough in the mixing bowl and refrigerate for 30 -35 minutes (to allow the chocolate to set).

Preheat the oven to 350°F. Line two baking sheets with parchment paper and set aside.

Use a 2 tablespoon scoop to portion dough. Roll dough into balls and place 12 balls on each baking sheet. Bake for 8-10 minutes, until the edges are set but centers are still soft.

Cool the cookies for 5 minutes on the baking sheets then transfer them to wire racks to cool completely. Repeat with remaining dough.

Sift powdered sugar into a medium bowl. Add vanilla extract, milk, and a dash of cinnamon. Whisk until smooth and spread across the tops of the cooled cookies.