½ cup plus 2 tablespoons unsalted butter, at room temperature
1¼ cups unbleached all-purpose flour
1 tablespoon instant coffee granules
½ cup confectioners' sugar, sifted
¼ teaspoon salt
½ teaspoon vanilla extract
1 cup semisweet chocolate chips
Preheat the oven to 325ºF.
Place the butter, flour, coffee, sugar, salt and vanilla in a mixing bowl. With the paddle attachment, beat the mixture together until smooth. Add the chocolate chips and stir just to incorporate.
Press the dough evenly into an ungreased 8-inch square pan. Using the tip of a sharp paring knife, score the dough into 16 squares. (These are quite rich, so I cut them into 24 rectangles.) Prick each a few times with the tines of a fork.
Bake just until the dough is set and beginning to color, about 30-35 minutes. Let cool a few minutes, then retrace the scored lines with the tip of the knife. Cool completely in the pan. Remove from the pan and store in an airtight container up to 1 week.