Butter an 8-inch square glass baking dish. Cut enough bread into 3/4-inch cubes to measure 6 cups. Chop chocolate.
In a small heavy saucepan bring 1 cup cream just to a boil and add chocolate. Remove pan from heat and let mixture stand, covered, undisturbed. In another small heavy saucepan bring milk and remaining cup cream to a gentle simmer. In a bowl with an electric mixer beat together whole eggs, yolks, sugar, and a pinch salt on medium speed 5 minutes. With mixer running, add milk mixture in a slow stream, beating until combined well. Whisk chocolate mixture until smooth and add with vanilla to egg mixture. Beat mixture until combined well.
Arrange bread cubes in baking dish. Pour cream mixture over bread and with a spoon push bread down into mixture to coat evenly. Chill pudding, covered, 1 1/2 hours.
Preheat oven to 350°F.
Put baking dish in a large baking pan and add enough hot water to pan to reach halfway up sides of dish. Bake pudding in middle of oven 45 to 50 minutes, or until set and springy to the touch. Transfer pudding to a rack and cool 30 minutes before serving.