The best dessert I had in Paris, recommended by my friend who lived there, was actually in a nice restaurant in the
Louvre. If you go to the Louvre, there's a nice restaurant out of the way up near the entrance to Napoleon III's apartments, I think on the third floor. It's not a very high traffic area, but the restaurant is a nice sit down one and the best desserts I had in France were there. Oh my goodness...so amazing.