In a small saucepan, bring ingredients for the homemade cherry simple syrup to a boil over high heat. Stir to dissolve sugar and remove from heat. Cover and let steep 30 minutes. Drain out cherries and save simple syrup.

Chill simple syrup completely before assembling cocktails.

Divide blueberries and mint leaves between two cocktail glasses. Use the muddler to gently crush the mint leaves.

Stir in 2 ounces of rum into each glass, as well as half the lime juice.

Fill each glass with ice.

Top with club soda and garnish as desired with fresh blueberries, fresh cherries and mint leaves.

Serve immediately.