No one seems to know where it came from or when it appeared, although it's been around for at least 15 years. Today, caffè shakerato is an Italian summertime favorite, served in bars throughout the country. Shaken, not stirred, it is the greatest version of iced coffee I have ever encountered. Caffè shakerato has taken over most of the territory previously occupied by prepared-in-advance-and-chilled caffè freddo (cold coffee), which was never really cold enough and usually tasted stale. A shakerato is easy to make at home (dust off your cocktail shaker!), but I'm sure that in time it will appear in Italianate coffee bars worldwide.
I asked a number of expert bariste (bartenders) how to prepare the perfect caffè shakerato, and they were all in agreement on the basics: Pour a shot of just-made espresso into a cocktail shaker half-filled with ice cubes. Those who like sweetened coffee should add some sugar syrup (preferable to granulated sugar, which dissolves poorly in cold water). Some like to add a little vanilla, vanilla syrup, coffee liqueur, or even a twist of orange or lemon peel. Agitate the cocktail shaker with the customary motions (shakerato means shaken) and strain the contents into a cocktail glass or champagne flute. The chilled and aerated coffee will be topped with a golden froth that is looser and lighter than crema (the compact layer of bubbles that floats on an espresso). I've provided a recipe that you can send to your coffee-loving friends.
The recipe can be doubled but making more than two at a time isn't easy--it's best to repeat the process.
¼ cup sugar
¼ cup water
2 large or 4 small ice cubes
1 freshly made espresso, preferably with Illy
Dissolve sugar in water over high heat. Cool syrup.
Put ice cubes in a metal cocktail shaker. Add ½ teaspoon (or more) sugar syrup, then pour the hot espresso over the cubes. Close shaker and shake it vigorously until the ice cubes are almost completely melted. You'll know from the sound. Strain into a stemmed glass-martini or champagne flute.
Every barista I spoke to serves caffè shakerato black, but I foresee the day of the tall-skinny-decaf-latte shakerato in my culinary crystal ball.