In a small saucepan, whisk together water and cornstarch until smooth. Add sugar, lemon juice, zest and egg yolks; cook over medium heat, whisking constantly, until mixture comes to a full boil. Boil for 15 seconds. Remove the pan from the heat and pour lemon mixture into a large bowl. Let cool slightly. cover surface with plastic wrap and refrigerate for 2 hours, or until chilled.

When chilled, whisk lemon mixture until smooth. Whisk in yogurt.

In the bowl of an electric mixer, beat cream on medium speed until stiff peaks form. Gently fold into lemon-yogurt mixture.

Arrange half of the berries in 6 parfait glasses or large wine glasses. Top with half of the lemon fool, then layer with remaining berries and lemon fool. To serve, garnish with whole berries, mint sprigs, and grated lemon zest.