The classic Moscow Mule is a simple, refreshing cocktail that combines vodka, ginger beer and fresh lime juice and is traditionally served in an ice-cold copper mug. The drink dates back to the middle of the 20th century, but it officially charmed its way into drinkers' hearts when the cocktail proliferated at bars in the early 2000s. Now, it's difficult to find a bar that doesn't offer the Moscow Mule, either on its menu or as an off-menu call. Of course, like any simple classic, it has spurred endless variations over the years. Barkeeps will switch the base spirit, making their own ginger beer and experimenting with fruits, herbs and other ingredients. Case in point: the London Mule. This variation, sometimes called a Foghorn, eschews vodka for gin, letting the juniper-dominant spirit meld with spicy-sweet ginger beer and tart citrus. Named for the gin, which historically hails from England, the London Mule is an easy variation that will keep you coming back for more. It's difficult to fudge this drink, but high-quality ingredients are key. Choose a London dry gin if you like the bracing bite of juniper, or try a more contemporary style if you prefer your gins to lead with citrus or other botanicals. Whichever route you go, make sure to unite that gin with good ginger beer and fresh lime juice to create the best-tasting drink. And serve in a copper mug, if you have one, to keep it cold from start to finish. If you like the London Mule, chances are strong that you will also like the Gin-Gin Mule, which was popularized at the famous New York bar Pegu Club. It's a slight variation that features fresh mint and a little simple syrup alongside the gin, ginger and lime. The History and Secrets of the Moscow Mule