I wondered about this so I googled it and found this!
The Dry Shake and The Reverse Dry Shake
As explained by James Fowler -
A "dry shake" refers to shaking ingredients in a cocktail shaker without ice.
Any recipe containing egg requires a vigorous dry shake for at least 30 seconds to ensure that the egg white combines with the other ingredients and produces a smooth, frothy texture.
After dry shaking, ice is added, and the mixture is shaken for a second time before being strained and served.
The reverse dry shake is the same technique but in reverse and is used in classic cocktails like a Whisky Sour or Ramos Gin Fizz.
All ingredients except the egg white are added to a shaker with ice and then strained to remove the ice. The egg white is added before the second shake, producing a more consistent foamy texture.
This was not what I was expecting. It is like a gin daiquiri and a mojito had a child. Mint is strong, but not overpowering. Very refreshful and perfect in afternoon or would be great at a brunch. Wow.