Make the shortbread cookies:

1. In a medium bowl, whisk together flour, cocoa powder, and salt. Set aside.
2. Cream butter and sugar together using a stand mixer fitted with the paddle attachment (or in a large mixing bowl with a hand mixer) on medium speed until light and fluffy, about 2 minutes.
3. Gradually add the dry ingredients and beat on low speed until just combined, about 30 seconds. The dough will be soft and slightly sticky but you should be able to easily shape the dough into a ball using your hands.
4. Use your hands to shape the dough into a disc and wrap it tightly in plastic cling wrap. Chill until firm, at least 30 minutes to an hour.
5. Line a large cookie sheet lined with a silicone baking mat or parchment paper. Set aside.
6. Remove the dough from refrigerator and transfer to a lightly floured surface. Use a rolling pin to roll the dough out until it is ¼-inch thick. Use Christmas cookie cutters (or other cookie cutters) to cut out different the cookies.
7. Transfer the cookies to the lined cookie sheet, placing them 1-inch apart. Re-roll any scraps and repeat to cut out more cookies.
8. Preheat the oven to 350 F. While the oven is preheating, transfer the cookie sheet into the refrigerator to chill (about 10 minutes).
9. Bake cookies for 10-12 minutes. Leave the on the baking sheet for 5 minutes before transferring them onto a wire cooling rack to cool completely.

Drizzle chocolate (optional):

1. Once the cookies have cooled, melt the chocolate in a double broiler on the stove or in the microwave. 
   • On the stove: Bring 2 inches of water to a low simmer in a saucepan over medium-low heat. Then, turn the heat to low and place a medium heatproof bowl on the mouth of the pot. Make sure that there is a gap of a few inches in between the bottom of the bowl and the water (You can also place a bowl on a steamer attachment on top of your pot). Add the chocolate and stir constantly as it melts. Stir until the chocolate is completely smooth and melted. This should take a few minutes.
   • In the microwave: The second way to melt chocolate (and an easier way) is in the microwave. Place the medium heatproof bowl of chocolate into the microwave and microwave in 30 second intervals. Remove the bowl at each interval and stir well. Repeat until the chocolate has completely melted. Stir until completely smooth.
2. Add a drizzle of chocolate over the cookies. Allow the chocolate to set, and serve.