Whether bartending on the job, bartending for friends at home, or if you hang out with a certain Mr. James Bond, you will frequently come across the question, “shaken or stirred?”
This question does require a lot of thought as it applies to so many more drinks than just the vodka or gin martini. First of all there are a few different ways to make a drink in general. There is the BUILT drink which means pouring the ingredients in order, directly into the glass you will be serving it in. For example a highball like rum and coke, or a long island iced tea. There is the FROZEN or blended drink which of course means blending the drink with ice, such as a pina colada or margarita. Then there are the SHAKEN and STIRRED drinks which do tend to raise the most arguments.
Now, when dealing with these types of drinks they are usually going to be martinis, all though there are drinks like the mai tai that are shaken but are poured or strained into a rocks or zombie glass. All cocktail recipes are different and unusual.
Traditionally martinis were always stirred which of course I feel is the reason for that to be the standard, meaning stir unless otherwise specified. The reason why martinis were always stirred was because people felt that shaking would "bruise" the gin. There is no way to actually “bruise” gin, but purists will fight this one to the death so I will leave that alone. All I can say is that shaking produces ice chips which will make the martini cloudier than usual.
When mixing a martini, shaking and stirring will produce different temperatures in your drink because stirring melts the ice and shaking cracks the ice. I recently saw a test done showing that stirring will produce a cold drink but shaking produces a much colder drink. Furthermore, the way a drink is shaken will produce colder results. So a light quick shake will not be as cold as a thorough hard shake. If you are going for the coldest possible drink you will want to shake hard but with a certain technique, which is more of a hard slashing motion.
Think of it like hammering a nail into a board, slower on the way up with a fast swing down and a quick stop, which causes the ice to crash into the bottom of the shaker. This will cause the ice to break apart and shatter in the liquid, producing a slushier drink but not as slushy as a blended drink.