Combine cold butter and brown and white sugar in a bowl.
Cream the butter and sugar until light and fluffy.
Add flour, chopped chocolate, and pistachios.
Combine until fully incorporated.
Divide the shortbread cookie dough into two logs then wrap with plastic wrap and refrigerate.
Using a serrated knife, cut the cookies then place on a parchment lined baking sheet.
Bake until golden brown, but the centers should not be fully set. They’ll firm up as they cool.
These cookies are delicious on their own or with a cup of coffee!