Preheat your oven to 350°F (175°C) and line a baking sheet with parchment paper.

In a bowl, whisk together the flour, baking soda, salt, and ground cinnamon. Set aside.

In a large mixing bowl, beat the softened butter, granulated sugar, and brown sugar together until light and fluffy, about 2-3 minutes.

Beat in the eggs one at a time, and then mix in the vanilla extract until well combined.

Gradually add the dry ingredient mixture to the wet mixture, mixing until just combined.

Gently fold in the cocoa powder, mixing well until the dough is uniformly combined.

Roll the dough into 1-inch balls and then roll them in granulated sugar before placing them on the prepared baking sheet.

Bake for 10-12 minutes, or until the cookies are set but still soft in the middle. Let them cool on the baking sheet for a few minutes before transferring them to a wire rack to cool completely.