In a 3-quart saucepan combine lambic, blackberries, apricots, and the 1/2 cup sugar. Bring to boiling; reduce heat. Cover and simmer for 5 minutes.
Meanwhile, for topping, in a bowl combine flour, the 1/4 cup sugar, the baking powder, and salt. Cut in butter until the mixture resembles coarse crumbs. Add milk and sage to flour mixture, stirring just until moistened. Drop topping into 6 mounds on top of hot filling. Cover and simmer about 15 minutes or until a toothpick inserted in topping comes out clean. Serve warm and, if desired, with whipped cream.