Add the lime, mint leaves, and simple syrup to a cocktail shaker and muddle until the lime has released its juice and the mint leaves have broken up-- about 15 seconds.
Add the gin and gently stir to combine.
Strain into a highball glass filled with ice.
Top with club soda and garnish with a lime wheel and mint leaves. Enjoy immediately.
Notes
To make simple syrup, combine equal parts sugar and water (I usually do ½ cup of each) in a small saucepan. Bring to a boil and cook until the sugar has fully dissolved. Let cool and then store in an airtight container in the fridge until ready to use. Discard after seven days.
If you don’t have a muddler, the back of a wooden spoon works as well!
To make these drinks ahead of time, work up to step two and then place the mixture in the fridge until you’re ready to continue.
I recommend using a smooth and herbaceous gin like The Botanist, but Bombay Sapphire and Hendricks would also be delicious. Try to avoid floral gins (like Roku) or dry gins (like Hayman’s Old Tom).