Talking head Rachel Maddow turned us on to this drink in her weekly cocktail segment on The Rachel Maddow Show. She uses David Wondrich’s version, published in his book Imbibe!
Rachel suggests separately adding a teaspoon of granulated sugar and a splash of water, rather than using simple syrup. This method seems to extract a lot more minty flavor with a lot less muddling; perhaps the sugar crystals aid in releasing the mint’s oils without damaging the rest of the leaf.
The amount of sweetener you use in this drink is highly personal topic; start out with the amounts we recommend and experiment until it tastes refreshing, but not syrupy-sweet. If you do choose to use granulated sugar, use half the amount listed for simple syrup.
Add the simple syrup (or the granulated sugar and a bit of water) to the shaker. Add the mint. Muddle it – not enough to tear the leaves, just enough to get everything mixed up and the oils released from the mint leaves. Add the spirits and stir. Strain into a julep cup and top with crushed ice.
Garnish with a short straw and a fat mint sprig; slap it between your hands first to express its oils.