Working quickly before the ganache sets, fit a pastry bag with a medium (3/8-inch) 6- to 8-pronged star tip and then fill the bag with the ganache. (Alternatively, scoop the ganache into a large resealable plastic bag and snip off one corner of the bag.) Hold the tip of the bag perpendicular to the cookie and pipe a rosette (or, if you will, a delicate blob) into the indentation in the cookie by moving the bag in a tight circle. Quickly pull the bag up or to the side to form a delicate peak. (Alternatively, use a teaspoon to dollop the filling in the indentation.) Repeat with the remaining cookies and filling. Top each cookie with a piece of coarsely chopped hazelnut or a single silver dragée if you prefer more glitz. Serve at room temperature. (The filled cookies should be stored in the fridge for no more than 2 to 3 days or they will get quite soft.) Originally published July 27, 2009.