01 - In a cocktail shaker or large glass, gently muddle the fresh raspberries and cranberries until thoroughly crushed and their juices are released.
02 - Add the cranberry juice, raspberry juice, initial portion of simple syrup (1 tablespoon), and fresh lime juice to the shaker. Stir or shake vigorously to combine all components.
03 - Fill two serving glasses with ice. Carefully strain the blended mixture into the prepared glasses, distributing any desired fruit pulp evenly.
04 - Gently pour chilled sparkling water or club soda over the mixture in each glass. Stir lightly to integrate.
05 - Taste the mocktail and add more simple syrup if a sweeter profile is desired.
06 - Embellish each mocktail with extra berries, a lime wheel, and a fresh mint sprig, as preferred. Serve immediately for optimal freshness.