Heat oven to 400 degrees. Combine sugar, flour, and salt in a bowl; make a well in the center. In another bowl, combine vanilla scrapings and butter. Add vanilla butter, egg whites, and cream to sugar mixture; combine. Using the large holes of a box grater, grate chocolate. Gently fold half the chocolate into batter; reserve remaining chocolate in a small bowl. Cover batter; chill at least 2 hours or overnight.
Trace a 4 1/2-inch circle onto a large, flexible plastic lid, such as one from a coffee can. Using scissors, cut lip from lid. Using a utility knife, cut out the traced circle to make a stencil.
Place a Silpat on work surface. Place stencil on Silpat. Using a spatula, spread about 2 teaspoons batter to fill circle. Repeat process, making three more circles. Remove stencil; transfer Silpat to baking sheet.
Transfer baking sheet to oven; bake 2 1/2 minutes. Rotate pan; bake 2 1/2 minutes more, or until golden brown. Working quickly, use a spatula to remove cookies from Silpat; roll each around the handle of a wooden spoon. Remove from spoon; let cool on wire rack. (If cookies harden before rolling, return tray to oven for 30 seconds or until pliable.)
Using a pastry bag fitted with a 3/8-inch plain round pastry tip, fill with coffee cream. Pipe cream into one end of cookie until it is full. Dip each end in chocolate shavings; serve immediately.
Store unfilled cookies in an airtight container up to 3 days.