Pour half a pint of Guinness stout into a pint glass. Then, prepare a shot glass by filling it halfway with the Irish whiskey, then floating Bailey's Irish cream on top of the whiskey until the shot glass is full.

Gather your friends around (or cry because you're drinking alone), and give each person a glass of the Guinness along with the whiskey/Bailey's shot. At the same time, everyone should drop the shot glass into the beer and slam the whole concoction. You _must_ drink it quickly, or the combination of beer and Bailey's will curdle. If you drink it at the right speed, it tastes like creamy chocolate milk heaven, and you'll want to do another one immediately. Which you should.

You don't need to use Guinness/Jameson/Bailey's specifically, but this is the canonical Irish version. I've used Murphy's stout instead of Guinness, and Canadian whiskey instead of Irish, and it tastes fine...but you don't want to push it. The beer absolutely must be a creamy stout.

Cheers!