I walked southeast along rue Turgot, passed through a triangular "square", turned south onto rue de Rochechouart, then continued along rue Cadet.

This patisserie is most likely Petit Jean-Francois, located at 3, rue de Rochechouart 75009.
I think it may have been called Aurore-Capucine Patisserie when I was there in 2006

http://gridskipper.com/travel/paris/aurorecapucine-patisserie-184333.php