To start, place your serving glass in the refrigerator, so that it is fully chilled by the time you are ready to pour your drink in and serve it. A martini glass will work best for this drink, but you can also use a bucket glass, or any other type of bar glass you prefer.
Now, while the serving glass is cooling away, take a cocktail mixing glass, and fill half of it with ice cubes. You can also use crushed or cracked ice for this purpose, but that might water your drink down a little, so if you are looking for a particularly potent concoction, stick to regular ice cubes.
Next, start preparing the drink. Pour 1 ½ ounces of gin into the mixing glass – pretty much any brand will do, as long as you use good-quality gin. Genever and London Dry are both great options.
Then, add in 1 ½ ounces of sweet vermouth and 1 tablespoon of yellow Chartreuse to the mixing glass. Use a stirring rod to swirl this mixture about for few seconds, until all the ingredients are well-mixed and the drink is thoroughly blended.
Once this is done, your San Marin cocktail is ready. Take your chilled serving glass out of the refrigerator, hold a strainer over it, and pour in the mixed drink. Finally, use a twist of lemon peel to garnish your drink, and serve chilled.