How to Dry Shake
When making drinks containing cream and eggs it is common practice to first shake the mixture without ice, before shaking the drink a second time with ice. This practice is known as 'dry shaking' and the theory is that first shaking without ice, and so at a higher temperature, better allows the drink to emulsify producing more aeration and a thicker foam on top of the finished cocktail.
Dry shaking is not a new technique and was first referenced by Ted Saucier in his 1951 Bottoms Up book in his recipe for a Hotel Georgia cocktail, "Shake well before adding ice. This gives a nice "top." Then add ice to chill, and serve in cocktail glass."
Some bartenders also place a spring from a Hawthorne strainer in the shaker during the first 'dry shake' as this acts as a whisk inside the shaker when the drink is shaken. I find the use of a spring unnecessary, and if used, it's a faff to clean.
Dry shaking does indeed produce more foam than conventional shaking with ice. But not as much as 'reverse dry shaking' does. Aristotelis Papadopoulos ("Telis" to his friends) from Thessaloniki in Greece claims to have discovered the benefits of this technique circa 2008.
To reverse dry shake: Combine all your ingredients in the shaker and shake conventionally with ice. Then open your shaker and strain the liquid back into the smaller tin (supposing you've followed my advice and used a two-piece shaker). Discard the ice left in the large tin. Reseal your shaker and bristly shake again without ice. Importantly, pour your drink into the glass through a fine strainer to catch any curdled egg, the chalaza (the tissue that connects the yolk to the shell's membrane), and ensure your foam has a pleasing light texture rather than looking like a floating meringue.
In my recipes, I tend to write reverse dry shake as follows:
"SHAKE all ingredients with ice and strain back into shaker. DRY SHAKE (without ice) and fine strain into chilled glass."