Combine first 7 ingredients, stirring well with a whisk. Arrange the bread slices in a single layer in a large shallow dish. Pour milk mixture over bread, and let stand until milk is absorbed (about 2 minutes).
Melt 2 tablespoons butter in a large cast-iron skillet over medium heat. Arrange 8 bread slices in pan; cook 3 minutes on each side or until bread is golden brown. Remove from pan; keep warm. Repeat procedure with remaining 2 tablespoons butter and 8 bread slices.
Combine 2 cups water, wine, 1/4 cup granulated sugar, and cornstarch in a large saucepan, stirring with a whisk. Bring to a boil; cook until reduced to 1 cup (about 5 minutes). Remove pan from heat. Add fruit to pan, stirring well to coat. Serve sauce with bread slices. Sprinkle each serving with powdered sugar.