Double Chocolate Croissant French Toast Casserole

Name: Double Chocolate Croissant French Toast Casserole
Ingredients: Cooking spray; 4 to 6 stale large croissants (10 to 12 ounces total); 1 (10-ounce) bag mini chocolate chips (about 1 1/2 cups), divided; 6 large eggs; 2 cups chocolate milk; 1 cup heavy cream; 3 tablespoons packed light or dark brown sugar (optional); 1 teaspoon vanilla extract; 1 teaspoon ground cinnamon; 1/2 teaspoon kosher salt; Whipped cream and maple syrup, for serving