With a potato peeler, shave off the lemon zest. Twist it over the glass to squeeze the essential oils into the cocktail. Garnish the cocktail with the zest and serve.
The Vesper is a variation of the Martini cocktail, and was invented by the writer Ian Fleming in the 1953 novel Casino Royale, in which secret agent James Bond names the cocktail in honour of Vesper Lynd, with whom he was in love. The famous character orders a Martini cocktail "shaken, not stirred". And so, from the pen of this great writer, the James Bond cocktail was born. The Vesper was scandalised at the time, because it was considered a desecration of the Martini, not so much for the addition of vodka, but precisely for the fact that the cocktail had to be shaken. A twist unthinkable at the time. And this is the great difference that makes it unique and inimitable, and so different from the original.