I am a dessert person and here are the best places to go for sweets in Paris.
I am going to start with Ladurée which is the top of the top in delicious salons de thé in Paris. Above all, the pastries are sensational. See the photos. I adore their viennoiseries. The croissants à l'ancienne are the best and I also love the bostocks (like a brioche toast that has been bathed in rum and almond flavor and is completely and absolutely superb. The bretzel is a delicious pate feuillettée with almonds and raisins in a pretzel form. The brioches are quite sensational. Next in line are all the delicious cakes and tartes. Whatever you choose, you will experience the best in quality. Of course, they are famous for their macarons and most people will be on line to choose a box full of a varied assortment. I am not a macaron fan but I know they are very good. There are four Ladurée destinations in Paris: in the department store, Printemps, the flagship store at the Place de la Concorde (terrible service), the shop in St. Germain des Près on rue Jacob (best service and beautiful decor) and on the Champs Elysées. The Champs Elysées branch is a proper restaurant which serves dinner whereas the other places close at about 7.
For chocolate pastries, rush over to Jean Paul Hevin. In my studied opinion these are probably the best in the world for creamy dark and delicious chocolate concoctions. Marquise, Choco-Passion, Chocolat-Framboise, Caracas, etc. etc. All are delicious and made of the best quality chocolates. Jean Paul Hevin has three shops--on rue Vavin in the 6th, a branch at La Motte Piquet-Grenelle, and a shop with a salon de thé near the Place Vendôme on rue St. Honoré. I am a regular as I can never get enough of the absolutely superb chocolate gateaux. I even love their macarons as they are all chocolate flavored with coffee, passion, lemon, etc. They are addictive!
In the 6th, near the Jardin du Luxembourg, you will find the superb maison of Christian Constant (rue d'Assas). Here, I like the little chocolates and the hot chocolate (the best in Paris) and the tablettes de chocolat. I prefer Hevin's cakes to those of Christian Constant but you will certainly find a few gems in his collection. I especially like the tarte au chocolat, le chocolat moka (with hints of coffee) and the feuilles d'automne. He has some wonderful non-chocolate items such as his pear tarte and the wonderful kalinka--a Russian cheesecake. As for the tablettes au chocolat, no shop makes such refined chocolate bars as that of Constant and it is difficult for me to choose which one I like the best.
When you think of chocolate, you think of La Maison du Chocolat but I don't. I have never been enamored of their cakes, candies or hot chocolates. It is a must-miss shop.
