Bring 1/2 cup Sherry to boil in a heavy small saucepan. Add currants. Remove from heat. Cover and let stand 15 minutes to plump.
Preheat oven to 325 degrees F. Butter an 8 inch square glass baking dish. Whisk milk, sugar, eggs, yolks, vanilla and cinnamon in large bowl. Arrange half of bread on bottom of prepared dish. Spoon Sherry and currants over. Arrange remaining bread over. Pour egg mixture over all. Let stand 15 minutes, pressing bread into egg mixture occasionally. Bake pudding until puffed and golden, about 1 hour 15 minutes. Transfer to rack.
Bring half and half to a simmer in heavy medium saucepan. Whisk yolks, sugar and cornstarch in medium bowl. Gradually whisk in hot half and half. Return mixture to same saucepan. Stir over medium heat until mixture thickens and leaves path on back of spoon, about 3 minutes. Strain into bowl. Stir in Sherry. Serve pudding warm with warm sauce.
c.1997, M.S. Milliken & S. Feniger, all rights reserved