A pair of Slippery Nipples
Well, alright then, not quite a pair.
Usually the Baileys is floated on top of the Sambuca [I've had black or white sambuca served to me in the past] in a shot glass.
My local pub had a special offer on girly drinks in intersting glasses before Christmas so I helped myself to a few. They work quite well with the black and white contrast in the drinks.
More often the drink is served with the Bailey's floated on top of the sambuca.