Melt chocolate with the shortening in a heatproof bowl set over a pan of simmering water, stirring occasionally.  Pour melted chocolate onto an 11 x 17-inch rimmed baking sheet.  Smooth with an offset spatula.  Refrigerate until chocolate is set but not brittle, about ten minutes.

Holding a sturdy metal spatula or a bench scraper at a 45° angle, scrape chocolate away from you to form curls.  If chocolate is too brittle, let stand at room temperature for 1 to 2 minutes before trying again.  If too soft, refrigerate briefly.  Break each curl into 1-inch pieces.  (Curls can be made ahead and refrigerated in an airtight container for up to 2 weeks.)

In a large bowl, combine mascarpone cheese, whipping cream, powdered sugar, and vanilla.  Beat with an electric mixer on medium to high speed just until soft peaks form.  Gently fold in liqueur.

Divide half of the ladyfinger cubes among six 6-ounce glasses.  (For smaller servings, use eight glasses.)  Drizzle with half of the espresso.  Top with half of the mascarpone mixture and half of the chocolate.  Repeat layers.

Cover and chill for 1 to 24 hours before serving.