Here is one of the many burning questions of the bar: When should a cocktail be shaken and when should it be stirred?
As you browse cocktail recipes you will notice that some instruct you to shake while others suggest that the drink be stirred. The debate of shaken versus stirred cocktails is hot, especially when talking about the famous Martini or any of the other spirit-only cocktail recipes out there.
Is there a theory behind which method to choose?
Yes, there is a general rule (as rules go in bartending). There are always exceptions, so it is best to follow a recipe's instructions or experiment with both to see which method makes the best cocktail in your eyes.
When to Shake...
Shake cocktails when they include fruit juices, cream liqueurs, simple syrup, sour mix, egg, dairy or any other thick or flavorful mixers. Essentially, use the shake whenever you need to ensure that every ingredient is fully integrated into the finished drink's flavor.
Shaking will create a strained drink with a cloudy, effervescent look at first that will clear up within a few minutes after straining. Due to the more violent nature of the shake, this method will also break down more ice and add a greater amount of water to the drink, which is desirable for getting a well-balanced cocktail.
A few shaken cocktails:
When to Stir...
Stir cocktails that include distilled spirits or very light mixers only. Stirring is a more gentle technique for mixing cocktails and is used to delicately combine the drinks with a perfect amount of dilution from the ice.
Many gin and whiskey cocktails are stirred because shaking is said to "bruise" the spirit (though that is also up for debate).
A few stirred cocktails:
This "rule" refers to cocktails and not necessarily mixed drinks that are built directly in the glass (think Vodka Tonic). These are almost always stirred and served with a sipstick or straw for further, fine-tuned stirring as the drink is consumed.
The point of either shaking or stirring (beyond mixing the ingredients, of course) is to add dilution to drinks from the ice. If either technique is done properly, the agitation will add the perfect amount of ice-cold water and bring your cocktails into balance.