Combine blueberries and raspberries in bowl. Add powdered sugar; gently toss to lightly coat.
Divide berry mixture among 6 (6-ounce) ungreased ovenproof custard cups or ramekins.
Whisk together sour cream and whipping cream in bowl. Spread about 3 tablespoons sour cream mixture onto each serving; sprinkle evenly with brown sugar.
Broil 4 inches from heat 2-3 minutes or until sugar is melted and caramelized.
- To make ahead, spoon berry mixture into dessert dishes; spread with sour cream mixture. Cover; refrigerate. Just before serving, sprinkle evenly with brown sugar. Broil as directed above.