Preheat oven to 325 degrees. Butter sides and bottom of 13x9" baking pan.
Butter one side of each bread slice and layer in pan alternately with croissants (6 slices bread, croissant slices, 6 slices bread).
In large bowl with an electric mixer set on med-high speed, beat eggs until slightly thickened, about 5 min.
Add sugar and vanilla and beat at med. speed until thoroughly combined.
reduce speed to low and add cream; mix until smooth.
Pour egg-cream mixture over bread and croissant slices. the slices will absorb egg-cream mixture slowly, so continue adding liquid until all is in pan.
In small bowl combine cinnamon, nutmeg and sugar. Sprinkle sugar-spice mixture over the bread pudding.
Fill a baking pan larger than the 13x9" bread pudding pan halfway up with hot water. Place in oven, set bread pudding pan in the water bath.
Bake 45-50 min. or until custard is set. When set, remove the bread pudding from the oven, and discard water in larger pan.
Cool to room temperature. refrigerate for 2 hours or until firm.