1/4 cup confectioner's sugar, or superfine sugar
2 Tbsp instant espresso powder, use 1 for a lighter coffee flavor
1 stick, 1/2 cup unsalted butter, room temperature and cut in pieces
1/2 tsp vanilla extract
1 or 2 tsp milk or half and half
1/2 cup dark chocolate chips
Preheat your oven to 325F. In the bowl of a stand mixer, briefly blend the dry ingredients. Add the butter and the vanilla to the dry ingredients and mix on low until the butter is incorporated. It will seem dry at first, until the butter has a chance to become thoroughly incorporated into the flour. Add in the milk or half and half a little at a time just until the dough comes together. Turn out onto a surface and mix in the chocolate chips with your hands, distributing well, but don't overwork the dough. Form the dough into a smooth 7 or 8 inch log, on top of parchment, plastic, or waxed paper. Roll the log of dough up with the paper and twist the ends to secure. Refrigerate for about 2 hours until firm. Slice the chilled dough into approximately 1/3 inch slices. Don't worry if the dough crumbles, just reform them on the baking sheet. Bake on a silpat or parchment lines baking sheet for about 12 minutes, depending on the thickness of your slices. Don't over bake, this shortbread should be silky and creamy, not crisp. Cool on a rack.