1 tablespoon instant espresso
1 tablespoon hot water
2 sticks (1 cup) unsalted butter, softened
⅔ cup confectioners’ sugar
½ teaspoon vanilla extract
2 cups all-purpose flour
4 ounces bittersweet chocolate, finely chopped
2 ounces semisweet chocolate, finely chopped, optional
Dissolve the espresso in the hot water and set aside to cool.
Using a stand mixer fitted with the paddle attachment, beat the butter and sugar on medium speed for about 3 minutes or until the mixture is smooth. Blend in the vanilla and espresso, then reduce speed to low. Mix in the flour, beating just until it disappears into the dough. Take care not to overwork the dough. Use a rubber spatula to fold in the chocolate. The dough will be soft and sticky.
Transfer the dough to a gallon-sized zip-top bag. Place the open bag on a flat surface and roll into a ¼-inch thick rectangle that’s about 9 x 10½ inches, occasionally turning the bag and lifting the plastic so as not to cause creases. You can also do this between two sheets of parchment. Seal the bag or wrap the dough in plastic wrap and refrigerate for at least 2 hours or up to 2 days.
Place oven racks in the upper third and lower third of your oven and heat the oven to 325º. Line two baking sheets with parchment or nonstick baking mats.
Cut the sides of the bag, then turn the dough onto a work surface and cut into desired shapes. You can use a ruler and a sharp knife to cut the dough into squares, or you can use a shaped cookie cutter if that’s the look you’re going for.
Transfer the cut dough to the baking sheets and carefully prick twice with a fork, gently pushing the tines all the way to the baking sheet. Bake for 16-20 minutes, rotating the sheets from top to bottom and front to back halfway through. The cookies will not take on much color in the oven. Transfer the cookies to a wire rack to cool completely.
If you would like to dip the cookies in chocolate, melt the 2 ounces of chocolate in a bowl set over a small saucepan of simmering water. Once the chocolate is just melted, dip each cookie halfway into the chocolate and then place on a sheet of parchment until the chocolate hardens. Store in an airtight container up to 4 days, or freeze (the ones not dipped in chocolate) up to 2 months.