Combine first 4 ingredients in a medium saucepan. Cook over medium-low heat 3 minutes or until chocolate melts, stirring constantly (do not boil).
Combine egg whites and egg in a large bowl; gradually add hot milk mixture to egg mixture, stirring constantly with a whisk. Stir in liqueur, vanilla, and salt. Add bread, tossing gently to coat.
Spoon mixture into an 8-inch square baking dish coated with cooking spray. Cover with foil; chill 30 minutes or up to 4 hours.
Preheat oven to 350°.
Sprinkle hazelnuts evenly over pudding. Place dish in a 13 x 9-inch baking pan; add hot water to pan to a depth of 1 inch. Bake, covered, at 350° for 30 minutes. Uncover and bake an additional 5 minutes or until a knife inserted in center comes out clean. Serve each bread pudding piece warm with 1/4 cup ice cream.