With a torch, light the rosemary sprig, place a coupe glass over it to fill it with smoke, and set aside.
Add the gin and citric acid to a shaker filled with ice and shake.
Double-strain into the prepared glass.
Top with the lavender-infused soda water.
Garnish with edible flowers.
*Lavender-infused soda water: Boil 30 oz water and 1/2 cup lavender syrup in a pot for 1 hour. Strain and let cool in the refrigerator for 3 hours. Add to a SodaStream (or similar soda maker) container and carbonate.