Chocolate shortbread:

1 3/4 cups + 1.5 Tbsp. All-purpose flour
1 cup + 1.5 Tbsp. Unsweetened alkalized cocoa powder
3/8 tsp. Baking soda
8 oz. Unsalted butter
2 tsp. Kosher salt
3/4 cups + 1 Tbsp. Granulated sugar

Place the flour in a medium bowl, sift in the cocoa and baking soda, and whisk to combine. Place the butter in the bowl of a stand mixer fitted with the paddle attachment. Turn to medium-low speed and mix until smooth. Add the salt and mix for another 15-30 seconds. Add the sugar and mix for about 2 minutes until fluffy. Add the dry ingredients in 2 additions, then mix until the dough begins to come together. Using your hands, mound together into a small, flat block. Wrap in saran wrap and refrigerate for at least 1 hour.

Preheat oven to 325 degrees fahrenheit. With a rolling pin, pound the top of the dough working from left to right, to begin to flatten it, then turn the dough and repeat (this will prevent the dough from cracking as it is rolled). If the dough does crack, use your hands to roll it into a ball and try rolling it out again. I've found that as the dough cools, it softens and is easier to work with.

Bake for 15-17 minutes, turning the pans halfway through baking. Let cool for 5 minutes and transfer to cooling rack.

Roll the dough as thin as you'd like
The dough can be refrigerated for up to two days
Cookie cutters are from Orson Gygi

Filling:

You can use a vanilla bean buttercream, cream cheese frosting, chocolate buttercream or white chocolate ganache for the filling. My favorite is the vanilla bean buttercream.