Place 1 cup of the blueberries in a small bowl and use the back of spoon to coarsely mash them. In a second bowl, whip the cream until soft peaks form. Add the icing sugar and beat until stiff peaks form. Whisk in the yogurt.
Add the mashed blueberries and ¾ cup of the remaining whole blueberries to the whipped cream mixture. Now add the cubed kiwi, reserving a quarter for garnish.
Fold blueberries and kiwi into the whipped cream mixture. Divide fool mixture between 4, 8oz. (250mL) decorative glasses or mason jars. Wrap and refrigerate until ready to serve. Fools can be made an hour or two before serving.
To serve, garnish the top of each fool with a few whole blueberries and cubed kiwi. Top each fool with a mint sprig.