There's only one thing on the menu at this famous St. Germain eatery: entrecote (rib) steak in a wonderful secret sauce, accompanied by a simple salad with walnuts and mustard vinaigrette, and piles of pommes frites. They don't take reservations, but the line moves quickly especially if you are a small party.
I had eaten the same menu at the Relais de Venise, the original restaurant established by the owner's father, now run by her sister, two years ago. Although they use the same recipes, I found the dinner at the older eatery better. Maybe it was just me. It was a little overheated in the restaurant tonight, and I couldn't give the food my whole attention.
Make no mistake about it, it is delicious and the portions are generous. The servers in their cute classic black and white uniforms come around twice. While you don't get a choice as to your main meal, they do have an extensive dessert menu. I'm partial to the profiteroles.
Some people pooh-pooh this place as a tourist trap. Yes, you'll hear mostly English and Italian at the St. Germain location; the other location is favored by locals. The long lines don't lie. It's worth the trip.