Muddle the mint leaves with the lemon juice in a shaker.
Add the London Dry gin and simple syrup.
Add ice and shake.
Strain into a highball filled with crushed ice.
Garnish with a mint sprig and lemon zest.
Float the sloe gin over the top of the crushed ice.
Variation: swap the lemon zest for orange zest.
This cocktail tastes great with homemade sloe gin. To find out how to make your sloe gin at home click here.