On my recent list of seriously cheap restaurants in Paris, I left out one biggie - Flam's! Whoever thought that all-you-can-eat gluttony didn't exist in France hasn't been to this chain. A warning: Flam's is not to be frequented in warm weather, and if you are lactose intolerant you shouldn't bother. The first time, I went with a lactose-intolerant Jewish boy and needless to say, he did not have a pleasant experience. Why? The menu consists only of variations of the Alsacian speciality, tarte flambée (also known as Flammekueche - hence the name of the restaurant), the main components being cheese and lardons (chopped bacon). This is like a super-thin crust pizza, with a base of either sour cream or grated swiss cheese or both, plus additional toppings like bacon, onions, mushrooms, or other weekly specials. They are soooo good, especially when it's chilly out.
A photo of a "gratinée" on their website, although sadly the ones in the restaurants do not come with a side of wheat, flour, and shallots :(
The basic menu is about 12€ for a salad and unlimited tarte flambées, though they also have more extensive menus including dessert. I have never gone beyond the basic menu, however, because I always feel stuffed to the gills when I leave, and I can't imagine having something sweet on top of it! The tartes are served on the wooden tray used to cook them, and at Flam's, you can get between 4 and 6 slices per tarte depending upon how big the table is and how hungry you are. Traditionally you are supposed to start with the "lighter" ones, like just plain cheese, and move your way up to the heavier ones - with bacon, with mushrooms, with bacon and mushrooms. Nobody uses forks & knives to eat the slices - you roll em or fold em the way you like, and gobble them up while the cheese is still melting.
My main issue with Flam's is that I always feel so sick when I'm leaving. I'll usually quit well ahead of the rest of the table, but when I stand up to go I'll realize I've overdone it (yet again). But it's so hard to stop! They're crispy and crunchy, yet warm & melty! Hence my warning to avoid it in warm weather. In cold weather I can walk it off, so that by the time I'm home I feel much better. But in warm weather, like right now, it would be too heavy and awful. Also, the service is usually horrendous, which means that you will have a slower paced meal than you might like. This poses a problem if you are with a group of hungry frat boys who want to maximize their intake, or even if you just expect minimal basics like forks with your salads or napkins. It's the perfect place for groups, but I wouldn't bother if you're on your own or only 2 (unless you are a hungry frat boy or are going with a hungry frat boy). Reservations definitely required on the weekends.
There are locations all over France, though I have only been to the one at Les Halles:
62 rue des Lombards
01 42 21 10 30