Step 2

Preheat the oven to 350 degrees Fahrenheit.

Step 3

Place the flour, cocoa powder, baking soda, salt, and cinnamon into a medium bowl and whisk to combine. Set aside.

Step 4

In a separate bowl using a hand mixer or the bowl of a stand mixer fitted with the paddle attachment, beat together the butter and the sugar until light and fluffy, about 5 minutes. Add in the vanilla and the egg and beat until combined.

Step 5

Stir in the melted chocolate and add the flour in batches. Once combined place the dough onto a cutting board or countertop and form into 2 equal-sized logs. Chill in the refrigerator for 15 minutes.

Step 6

Place the chopped pistachios onto a baking sheet or into a baking dish and coat the sides, pressing the nuts in so that they stick to the cookie logs.

Step 7

Wrap the logs in parchment and then in plastic and freeze for up to a month. If baking immediately, freeze for about 10 minutes and then cut the cookie into 1/2 inch slices.

Step 8

Line two baking sheets with parchment and place the cookies 1-inch apart on the cookie sheet. Bake for 10-12 minutes until firm around the edges and slightly puffed in the center.

Step 9

Allow to cool completely and serve.