A traditional fool is a creamy dessert made with heavy cream and berries. For this low-fat version, a puree of raspberries, blackberries, and blueberries is added to berry yogurt and reduced-fat whipped topping.
In a small saucepan, combine raspberries, blackberries, blueberries, orange juice and sugar. Bring to a boil over high heat, then reduce heat to medium-high and simmer for 10 minutes. Carefully add fruit mixture to food processor and puree until smooth. Strain through a fine mesh strainer and place in the freezer for about 50 minutes, or until very cold.
Place thawed whipped topping in a medium-size bowl; fold in yogurt and cooled fruit puree until just combined. Serve immediately. Garnish with berries, if desired.