In a large bowl, whisk together egg yolks, milk, cream, sugar, vanilla, salt and nutmeg. Add toasted croissant pieces and chocolate. Mix to combine.
6 large egg yolks, 2 cups whole milk, 1 cup heavy cream, 1 cup granulated sugar, 1 tsp vanilla extract, 1/2 tsp kosher salt, 1/2 tsp ground nutmeg, 6 croissants (1 lb) cut into 1" pieces (it's okay if they are day old), toasted in the oven until they feel dry and hard, but are still very pale looking*, 4 oz bittersweet chocolate (70% cacao) chopped into chunks