For the Rosemary Simple Syrup: Combine water and sugar in a small saucepan over medium heat and stir until well combined and mixture has thickened slightly (about 5 minutes) Right before taking off the heat, stir in the rosemary, and remove from heat. Let cool for about an hour then remove rosemary and place in a seal-able container for storage in your refrigerator.
To assemble the cocktail: To assemble, muddle the strawberries with the bourbon in a glass until the strawberry juices have infused the alcohol. Strain with a fine strainer to minimize strawberry seeds in your drink. Fill two glasses generously with ice cubes and pour equal parts of the bourbon in each glass. Put 1 jigger (1.5 oz) of the Rosemary Simple Syrup in each glass and stir to combine. Top off with some sparkling water and garnish with rosemary or strawberries. Enjoy!