Blueberry/Raspberry Gratin

1½-1#190; pints combination blueberries and raspberries2 cups sour cream or plain or vanilla yogurt#190; cup packed brown sugar, divided1 teaspoon grated lemon zest2 teaspoons fresh lemon juice#188; cup brown sugar for glazeHeat broiler. Lightly butter a 10-inch square baking pan.Toss berries together and pour into a baking dish.In a medium bowl, mix together sour cream or yogurt, 1/2 cup brown sugar, lemon zest, and lemon juice. Spoon mixture evenly over berries. Sprinkle with remaining brown sugar. Wipe any residue mixture from around side of baking dish as this will blacken under broiler heat.lace dish under broiler and cook until sugar begins to caramelize - about 3 to 4 minutes - and topping begins to bubble. Spoon into individual dessert dishes while hot. Gratin may also be served over scoops of vanilla ice cream.Serves four to six.The Christian Science Monitor