Watermelon Slush

Cut the watermelon into 2-inch wedges. Remove and discard the rind, black seeds, and as many of the softer white seeds as possible. Cut into 1-inch chunks and place them in the bowl of a food processor or blender. Process until pureed although some small chunks may remain. Add the lemon or lime juice and sugar, and blend until just mixed Transfer the mixture to a stainless steel bowl, cover, and freeze until solid, for 8 to 10 hours. About 4 hours before serving, move the bowl to the refrigerator to soften. In the last hour before serving, use a fork to break the softened mixture into shavings. Serve the slush in pretty glasses or bowls. Garnish with a fresh sprig of mint if available.