In a shot glass, begin by pouring a layer of Kahlua.
Next, slowly add a layer of Bailey's Irish Cream Liqueur.
Last, pour a layer of Grand Marnier on the top.
(Optional) Serve with a flame on the top. *If you choose to set your shot on fire, be extra careful as the glass can become hot.
Notes
B-52 Cocktail - To turn this shot into a cocktail, just pour one ounce of each ingredient (rather than 1/3 an ounce) and serve it in a cocktail glass rather than a shot glass.
Layering Tips - Use a bar spoon or the back of a spoon to pour each layer more slowly. Pouring from a shot glass rather than a bottle also helps to pour more slowly. The slower your pour, the cleaner each layer will appear.
Variations - If you replace the Grand Marnier with Frangelico, it's a B-51. In the B-53 recipe, Sambuca replaces the Irish cream. If you substitute the Grand Marnier for Amaretto, it becomes the B-54.
Flame Tips - If you want to set your shot on fire, adding a thin layer of overproof rum to the top will help a lot.