Preheat oven to 350F. Place croissants on baking sheet.
Bake until lightly toasted, about 15 mins. Cool completely and cut into 1 inch pieces (should make about 14 cups).

Bring milk, cream, 1 cup sugar to simmer in heavy saucepan over medium heat, stirring until sugar dissolves.
Simmer 5 minutes, stirring occasionally. Remove from heat. Add vanilla.
Cover; let stand 5 mins.

Whisk eggs and remaining 1 cup of sugar in large bowl to blend.
Gradually whisk in hot milk mixture.
Strain custard through sieve into another larger bowl.

Place croissants in 13x9x2 inch glass baking dish. Sprinkle with chocolate chips.
Pour custard over croissants.
Let stand at room temperature 1 hour, gently pressing to submerge croissant pieces in custard.

Cover and refrigerate for 24 hrs.

Preheat oven to 350F. Place baking dish in large roasting pan.
Fill pan with enough boiling water to come halfway up sides of baking dish.
Bake until bread pudding is puffed and golden, about 45 mins.