Preheat oven to 350. Arrange croissant cubes on a large baking sheet. Bake until golden brown, about 10 minutes. Cool. Reduce oven temperature to 325.

Divide chocolate among six 3/4 cup custard cups. Top with croissant cubes, dividing equally. Pour 2 cups of cream into a heavy medium saucepan. Scrape in seeds from vanilla bean; add bean. Bring to a simmer over medium heat. Remove from heat. Whisk egg yolks and sugar in a medium bowl to blend. Gradually whisk in hot milk mixture. Discard vanilla bean. Pour custard over chocolate and croissants, dividing equally.

Place cups in a large baking pan. Add enough water to baking pan to come halfway up sides of cups. Bake puddings until set, about 40 minutes. Remove from water; cool slightly. Serve warm or at room temperature.