Pour a little of the ganache onto a flat plate. Dip the glass rim into the ganache, then dip into some shaved chocolate. Tap the glass while upside down to remove excess shavings, then place right-side up.
Add the Irish cream and vodka to the remaining ganache and whisk well. Fill a martini shaker three-quarters full with ice, and then pour the chocolate mixture in, and shake well for 30 seconds. Remove the lid and pour through the strainer of the shaker into the prepared glass, leaving about 1/4-inch of space from the rim of the glass.