“Every restaurant I visit nowadays has some sort of Moscow Mule on their cocktail menu. I’m not a huge vodka drinker, but I do love how it is served in those gorgeous copper mugs, so I thought to myself, “I need to whip this up with tequila.” If you have those copper mugs, use them for this. The metal keeps the cocktail cold for a very long time.”
Combine the serrano chile, sugar, water and mint in a small, heavy pot. Stir over medium heat until the sugar dissolves, about 2 minutes. Remove from the heat and let cool completely. Once the simple syrup is cooled, discard the serrano.
In a large pitcher, combine the tequila, lime juice and cooled simple syrup. Stir to combine.