Napoleon or mille-feuille, or other versions of the dessert is time-consuming if you create the puff pastry sheets from scratch. And Au Bon Pain probably did that. If you buy the sheets, however, then it is simply a question of mixing the paste (almond-paste or other similar stuff) and spreading it between the layers of puff pastry before baking.As was I. There are so many things that are like that - little things that happened in the history of a company that were there for a short period of time and, then, gone.
When I was a college kid in the '80s, the Au Bon Pain near the store I worked in came out with a Napoleon that was incredible. It was there for, maybe a year or so, and then gone.
When I asked what happened, they said it was complicated to make and store and not worth the limited demand they had for it. That was thirty five years ago. I'd bet almost no one but I - and a few other crazy fans of Au Bon Pain's brief flirtation with the Napoleon - even remember it once made one.
I've been promising myself that I will try my hand at making a tarte tatin from scratch (basically an apple pie with pastry layers) but it is time consuming, since one has to repeatedly fold and roll out the dough each day for something like fourteen days to create the layers! Oh well, maybe next year.