To make Shiso Leaf Simple Syrup: Heat equal parts water and sugar, stir to dissolve. Once boiling, add 4-5 Shiso leaves, return to boil, then turn off heat and allow to rest for 30 mins. Strain in to a glass jar and store in the refrigerator.
To make the cocktail: Mix all ingredients well in a shaker with ice. Strain into a glass with plenty of ice and garnish with a Leaf.