A couple of observations from a recent visit, not entirely devoted to the Left Bank, but this seemed like the best place to stick them.
So, the Left Bank. This is what I had to say about Les Papilles in 2007:
"Les Papilles (30 r. Guy Lussac). As mentioned on this board elsewhere this small restaurant/epicerie offers only one meal, altho you choose your wine from the shelves at 6 euros above retail. The dinner we had was very au bonne mere--leek pottage, lamb stew w/ primeurs, panna cotta--nothing that I could not make myself at home, but with an intensity of flavor I could never recapture chez moi. A memorable experience, particularly at 98 euros for the two of us."
Since then Les Papilles has been featured twice in the NY Times and popped up in all sorts of other places, so I reserved with some trepidation, feeling that it might have been thoroughly Anglicized by now. Once I arrived in Paris, however, I moved our reservation up from 7:30 to 9:30, and whether it was this more Paris-friendly dinner-hour or the one-meal-and-one-meal-only-served policy acting as a tourist-barrier, we were pretty much surrounded by French-speaking customers. Moreover, the meal was as good as I remembered--this time an eggplant bisque poured over feta cheese and crème fraiche, followed by pork belly braised in vegetables and beans, a cheese course, and a panna cotta dessert. A little pricier than the previous time (the exchange rate was pretty much of a disaster area), but still a satisfying venue for French comfort food.
And on the other bank, just above Boulevard Haussmann at the edge of Montmartre, is a place that anyone interested in the history of restaurants needs to visit. There were about 250 "bouillons" in Paris at the turn of the last century, and one of the few now remaining -- perhaps the last truly authentic one (i.e., it hasn't changed much in any respect since it opened in 1896), is restaurant Chartier (at 7, rue Faubourg Montmartre). I don't necessarily recommend this place for its food -- which is usually good, simple, and cheap -- and I do recommend that you go at lunch (for the experience) and not for dinner (where the food options elsewhere are so much better). If you do go, you'll get a unique chance to experience what a fast-food restaurant was like for average Parisian (and perhaps many other urban) workers in 1900. They have their own website here (http://www.restaurant-chartier.com/www/visit/
) which is, as might be expected, rather quaint, but a more informative review can be found here (http://www.davidlebovitz.com/2009/02/bouillon-chartier/
Anyway, I would no more recommend Chartier over, say, a starred restaurant for your one day in Paris than I would the catacombs over the Louvre. But if anyone were compiling a list of Parisian GNRs, I'd wager Chartier would be a charter member.