1. Add blueberries and sugar to a cocktail shaker and muddle until blueberries are well macerated. 2. Add lemon juice and whiskey and shake vigorously for 1 minutes. 3. Fill 2 cocktail glasses with ice, and strain over each evenly, shaking if needed to release all liquid. 4. Top each glass with seltzer water, and stir. 5. Garnish with fresh lemon and blueberries.