Cut bread in half diagonally. Arrange half of the slices in a single layer, overlapping if necessary, in an ungreased shallow 2-qt. microwave-safe dish. Drizzle with half of the chocolate; top with remaining bread.
In a 1-qt. microwave-safe bowl, combine the cream and milk; microwave, uncovered, on high for 2-4 minutes or until hot but not boiling.
In a small bowl, beat eggs; add sugar. Add a small amount of cream mixture; mix well. Return all to the larger bowl; stir in vanilla. Pour over bread; drizzle with the remaining chocolate.
Cover and microwave at 50% power for 9-11 minutes or until a knife inserted in the center comes out clean, rotating a half-turn one (mixture will be puff up during cooking). Uncover and let stand for 5 minutes. Serve warm or cold. Refrigerate leftovers.