I have been in Paris 3 times this year for work, and have sampled many-a salons and bistrot, and Carette, hands down, has the best service I have ever had in Paris.
Tucked between the Cafe Kleber and another bistrot, Carette was a bit hard to find if you are looking from across the street. Carette is a salon de thé, offering traditional French fare, patisserie, and vienoisserie at all hours.
I was here tonight with 3 colleagues. Upon entering, hearing us speaking English, the waitresses were just as happy serving us in English and French. She took the time to explain the specials, and the history of the salon (since the 1920s!). Throughout our meal the waitresses checked on us frequently (but you have to let them know if you need to pay).
My colleagues all had the French onion soup, which was good, and me being a vegetarian, had the salade végétarien. It was huge, and as salads go... not mind blowing. But it did have avocado and egg, on a bed of julienned carrots, raw potato, red cabbage, and haricots vert (green beans), smothered in what tasted like mayo. Considering that there was an egg, nutritionally speaking it was fine. But when it comes to taste... all I have to say is, meh. On top of that, it cost a whopping 17 euros. Maybe it's to pay for the labour of julienning all those carrots and potatoes... And the avocado. (To their defense they do have quiches and omlettes as well as sandwiches, and a veloute des legumes - vegetable soup)
Hearing that we missed tea-time, the waitress, at the end of our meal, brought us house-made little petit fours - a lemon meringue tartlette, a hazlenut chocolate carré, a fragrant shortbread button with fresh raspberries on top, a choux aux chocolate, and a praline tartlette, all on the house. Despite being a chatty bunch, we enjoyed them so much our table was silent for some moments.
Come for the delectable treats during tea time (3-6pm) when they have a formule (combo) - I will be returning for their famed chocolate Carette (and compare it to Angelina's).
However if you are vegetarian and looking for a good *meal*, there are better places to go.