- Stir together coffee liqueur or milk and espresso powder or coffee crystals in a small bowl or custard cup; set aside for a few minutes till coffee is dissolved.
- Beat butter in a large mixing bowl with an electric mixer on medium to high speed for 30 seconds. Add sugar and baking powder; beat until combined. Beat in liqueur mixture, egg, and melted chocolate until thoroughly combined. Beat in as much flour as you can. Stir in remaining flour.
- Cover and chill dough about 1 hour or until easy to handle. Shape dough into a 1-3/4-inch square log 10 inches long. Wrap in waxed paper or clear plastic wrap. Chill from 4 to 24 hours or until firm.
- Heat oven to 375 degree F. Slice dough into 1/4-inch-thick squares. Place 2 inches apart on an ungreased cookie sheet. Bake for 9 to 11 minutes or until edges are firm. Cool on cookie sheet for 1 minute. Transfer to wire racks and cool completely.
- Up to 1 hour before serving, spread flat side of half of the cookies with about 1 teaspoon Coffee Liqueur Icing. Top with remaining cookies, flat sides down. Store in the refrigerator until serving time. Makes 20 sandwiches.
From the Test Kitchen
Place in layers separated by waxed paper in an airtight container; cover. Store at room temperature up to 1 week or freeze up to 3 months. Thaw, then fill up to 1 hour before serving. Refrigerate until serving time.
Test Kitchen Tip:
Use a small metal spatula to smooth and square off the sides of the dough log.
Coffee Liqueur Icing
- Stir together instant coffee crystals and whipping cream in a small bowl until coffee is dissolved. Stir together the coffee mixture, powdered sugar, and coffee liqueur in a medium bowl. Add enough whipping cream (1 to 2 tablespoons), 1 teaspoon at a time, to make icing of spreading consistency.