The Seattle Times just wrote about the Vesper at The Doctor's Office in Seattle, WA, including a batch recipe. Their preference is Beefeater, Reyka vodka and Cocchi Americano, as well as a good slug of water and freezing it (instead of dilution via shaking).

https://www.seattletimes.com/pacific-nw-magazine/the-perfect-vesper-has-been-found-and-it-can-be-stored-in-your-freezer/