According to cocktail historians, this classic drink was created in the 1940s as a way to sell more vodka. The pairing of vodka, ginger beer, and lime juice was so refreshing that it's still a popular cocktail today, especially on a hot day.Traditionally, a Moscow Mule is served in a copper mug. When filled with ice, the mug becomes frosty cold, making the drink even more delightful on a hot day. (If you don't have copper mugs, a Collins glass is the best substitute.)Because the cocktail is made with so few ingredients, the quality of each component really matters. Many Moscow Mule recipes call for ginger ale, but we prefer using ginger beer, which has the hot and spicy bite of fresh ginger. Our Test Kitchen recommends Fever Tree or Fentimans brand ginger beer. And always use freshly squeezed, not bottled, lime juice. (While lime juice is a key ingredient in Moscow Mules, this rule applies to any cocktail.)Moscow Mules can be easily scaled up and turned into pitcher drinks for parties or other large gatherings. Simply pour the lime juice into a tall pitcher filled with ice, then pour in the ginger beer and vodka. Use a long-handled spoon to stir the cocktail before serving. Garnish the drinks with lime wedges.