In a medium bowl stir together the sour cream, powdered sweetener or powdered sugar, and liqueur or orange juice. Gently fold in dessert topping.
In 4 parfait glasses, layer half of the peaches, raspberries, blueberries, and sour cream mixture. Repeat layering. If desired, sprinkle grated chocolate over each serving. Serve parfaits immediately or cover and chill for up to 2 hours. Makes 4 servings.