1. In a saucepan, combine berries, 1/3 cup sugar, cornstarch, salt and lemon juice. Cook over medium-low heat, stirring often, until sugar dissolves, berries have softened and juices have thickened slightly, about 10 minutes. Remove from heat, transfer to a bowl and let cool, stirring occasionally. Cover and refrigerate until cold, about 1 hour.
2. In a chilled bowl, using an electric mixer with chilled beaters, beat cream and remaining 1 Tbsp. sugar until soft peaks form. Add yogurt and vanilla and beat until medium peaks form.
3. Using a large spatula, gently fold blueberry mixture into cream mixture until just barely combined, with streaks remaining. Divide mixture among 6 bowls, top with additional blueberries, if desired, and serve.