Combine flour, cocoa, and salt in a medium bowl; set aside.
Beat butter in a large bowl with an electric mixer on medium to high speed for 30 seconds.
Add sugar and beat about 2 minutes or until fluffy, scraping side of bowl occasionally.
Beat in egg and espresso powder.
Beat in as much of the flour mixture as you can with the mixer.
Stir in any remaining flour mixture (dough will be crumbly).
Use your hands to form the dough into a ball. Divide dough in half.
Preheat oven to 350°F
Roll each half of the dough to 1/4-inch thickness on a lightly floured surface.
Cut out shapes using a 2-1/2-inch star-shape cookie cutter.
Place 1 inch apart on ungreased cookie sheets.
Bake for 10 to 12 minutes or until edges are firm.
Transfer to wire racks and let cool.
Microwave chopped chocolate and shortening in a small microwave-safe bowl on 50 percent power about 2 minutes or until melted and smooth, stirring three times.
Dip one-third of each cookie into melted chocolate mixture; let excess drip back into bowl.
Place cookies on waxed paper; let stand about 1 hour or until set.
If desired, brush luster dust on chocolate.
Makes 48 cookies.
Place cookies in layers separated by pieces of waxed paper in an airtight container; cover. Store at room temperature for up to 3 days or freeze for up to 3 months. Thaw cookies, if frozen, before serving.