Preheat oven to 350 degrees Fahrenheit.

Combine flour, cocoa, cinnamon, and salt in a large bowl and set aside.

In the bowl of a stand mixer, add the margarine and beat until soft. Add the sugar and vanilla, blending the mixture until creamy. Reduce the mixer speed to low and add the dry ingredients, scraping down sides of the bowl periodically. Do not overbeat; cookie dough should be light with a crumby texture.

Divide dough into two large balls and wrap in plastic wrap. Chill for 30 minutes in the refrigerator.

Remove the dough and form each ball into a long log, taking care that they are even and thick.

Wrap each log in plastic wrap and chill them for an additional 30 minutes, this time in the freezer.

In a small bowl, whisk the egg yolk until smooth enough to be used as a glaze.

Spread the two tablespoons of sugar onto a piece of Gefen Parchment Paper.

Brush each log with a small amount of egg yolk and then roll them in the sugar until covered.

With a sharp knife, cut the logs into pieces about half an inch thick, creating the cookies. Bake cookies for 15-18 minutes.