Preheat broiler. In a bowl, whisk together sour cream and vanilla. Set aside.
Combine blueberries and blackberries and place them in the bottom of 4 individual ramekins. Top berries with sour cream mixture, allowing some of the berries to show through. Sprinkle 1 tsp brown sugar over each serving, breaking up any lumps.
Broil 3 minutes, until sugar melts (the top should be caramelized).
Instead of sour cream, try using Cool Whip topping.