In a medium bowl, mash with a fork 12 oz. raspberries (about 3 cups), 2 tbsp. sugar, and the liqueur, if using. Set aside.
In a large bowl, whip cream with remaining sugar using a mixer or whisk until firm peaks form. With a spatula, fold in raspberry-liqueur mixture. Divide fool among 8 glasses or bowls and top with remaining fresh raspberries. Serve immediately or cover and chill for up to 2 hours.
Note: Nutritional analysis is per serving.