In my case, I adore the French patisserie.
I think one must go to Paris, first and foremost, to be able to try the chausson aux pommes they bake in some special places (not all chaussons aux pommes are edible, mind!). But I love any other kind of patisserie (and boulangerie!).
The croissants au beurre are also some kind of treat which is difficult to describe. This, however, is very easy to find in all French cities and villages. It amazes me that such a popular patisserie which is delicious all over France (and also in ex-French territories, like Senegal, where I have eaten some of the best of my life) cannot be found in any city in Spain. What they call cruasanes here is some kind of horror that makes you sick only by smelling it.
And yes, you must speak French to go into a Boulangérie-Patisserie and ask almost absent-mindedly for your preferred food. Here is a tip:
YOU: 'Ssieux' dames!
PATISSIER: 'Jour, ssieu/madame. Vous désirez?
YOU: Un croissant au beurre, un pain au chocolat, un chausson aux pommes, svp.
PAT: Voilà.
YOU: Merci mssieur/madame. Bonne journée!
PAT: Merci. Bonne journée à vous aussi
In some popular restaurants (called brasseries, which means really bear shops) you may also end your meal with a wonderful tarte tatin (with crème fraiche, don't forget that!).
I have developped some appetite right now. So long, I'm going to have dinner!