St. Germain des Pres has more than its share of storied brasseries, bistros, restaurants and watering holes. If you'd like something smaller, more romantic and tucked away, (with outstanding food, by the way), then you'll be pleased with Bistro Mazarin. Intimately sized with the requisite terrace tables on a quiet corner of the street, you have now left the bright lights of a block or two away and traded them for a world of clinking silverware, French chatter, friendly laughter and everything else that makes for a fabulous, lingering Paris evening dinner.
Perhaps open with a glass of champagne; their house choice is dry and fine.
Meals are hearty and well prepared. Start out with oysters that you'll see being opened on the corner of the terrace as you walk in -- or a wonderful soup of the day or steak tartare. I highly recommend the salade gourmand, which includes such highlights as foie gras, duck confit and smoked duck; it is nothing short of marvelous! (Like all great Paris eating establishments, the best dishes can be seasonal so check the chalkboard for the day's features and you can't go wrong.)
For a main course, the cote du boeuf is generous and succulent -- or have leg of lamb, roasted chicken or a catch of the day. You may not have room for dessert, but you'll find some brief selections if you do. (I can't help you with that; my eyes stop looking whenever they see creme brulee on a menu and I never remember anything else...)
Bottom line: leave some of the well-traveled corners and their sometimes over-loved, well-known names behind you for an evening and you may discover a true treasure like Le Bistro Mazarin.