Fill a rocks glass with ice. Combine all the ingredients, except the soda water and garnish, in a cocktail shaker. Fill it two-thirds of the way up with ice. Cover and shake hard for 20 seconds. Strain the mixture into the glass over the ice. Add the garnish, and top with a dash of soda water.
60ml of Nasturtium gin
10ml of lemon balm liqueur
15ml of orgeat syrup
15ml of freshly squeezed lemon juice
A dash of soda water
Lemon zest, lemon balm (Melissa officinalis) leaf,
Nasturtium leaf, to garnish