Knowing the ingredients of any given cocktail is only half the battle. You've got to nail down the proper way to mix them together, too.
Shaking your drink with ice gets it extraordinarily cold and thoroughly mixed. That's perfect for drinks with juice, dairy, or egg whites since it's a more aggressive way of mixing that allows spirits to be incorporated into thicker liquids. Plus, it makes you look like a pro.
Shaking also aerates cocktails for a frothy pour, and the tiny air bubbles that are created in the process help to cut excessive sweetness from juice.
For drinks that only contain spirits, careful stirring is the proper way to mix since the ingredients are incorporated but not roughed up. The clarity and strength of the liquors are kept intact while still mixing thoroughly with whatever other spirits are included.
It might seem like overkill, but trust us: a perfectly stirred Manhattan or Old Fashioned is clear, strong, and beautiful. Try shaking them and you’ll end up with a cloudy, unattractive mess that doesn’t taste much better than it looks.
The Bottom Line
While each method has its advantages, they're not interchangeable.
Stirring a cocktail that's meant to be shaken won't properly incorporate the heavier elements, so you'll end up with a poorly mixed drink.
Shaking a stirred cocktail is even worse: you’ll be left with an opaque mess of a drink, as opposed to the precise creation that comes from careful stirring. Connoisseurs will also say that liquor is "bruised" in the process of shaking, which compromises the taste of complex booze. And maybe most importantly, it’ll get you drunk much less quickly, since the ice that's being shaken will break dilute your cocktail to almost half its intended strength (and taste).
So despite what you've learned from Bond movies, never order your martinis – or any other stirred drinks – shaken. Invest in tools for both and make sure you know when to use ‘em, and your cocktails will be noticeably better. Plus, you’ll earn some bragging rights at your next party.