01 - In a small saucepan, combine sugar and water. Heat gently over medium heat, stirring constantly until sugar dissolves completely. Remove from heat and allow to cool to room temperature.
02 - Place raspberries in a blender or food processor. Blend until completely smooth.
03 - Press the raspberry puree through a fine mesh sieve into a bowl to remove seeds, using the back of a spoon to extract maximum puree.
04 - Stir cooled sugar syrup, lemon juice, and raspberry liqueur if using into the seedless raspberry puree. Mix thoroughly until well combined.
05 - Pour mixture into a shallow, freezer-safe container. Freeze for 1 hour.
06 - After 1 hour, use a fork to scrape and stir the mixture, breaking up any ice crystals forming around the edges. Return to freezer and repeat this process every 30 to 45 minutes for 3 additional hours until sorbet reaches a smooth, scoopable consistency.
07 - Serve in chilled bowls or glasses, garnished with fresh raspberries and mint leaves if desired.