Desserts in French restaurants are much more variable than the other courses. They are often exceptional, yet often in cheaper restaurants too little effort is made.
Ile flottante requires some effort to get it right, and is frankly not great if you get it wrong. The apple tart and cherry cake here are extremely easy and reliable to make.
One slight gripe I have relates to cream in aerosol canisters. I don't know how this is prepared but I don't think it ever matches 'real' cream, although the canisters are popular in France, as elsewhere. Many a 'budget' restaurant will squirt this cream on a dessert to make it look more glamorous. Doesn't work for me, please try and avoid it.
Cherry Cake - too many cherries? try this very quick and easy recipe
Apple tart - the absolute staple of every french restaurant
Ile flottante - the other absolute staple of every french restaurant!
Creme brulee - blowtorch optional for this delicious dessert
Chocolate mousse (mousse au chocolat) - yum!
Sabayon - delicious fluffy custard originating from Venice
We have a farm nearby that makes their own ice-cream, and sells it more cheaply than many supermarket ice-creams. I haven't grasped the recipe or method yet, but if you have the chance to try real, fresh, home-made ice-cream, do.
...and a recipe that isn't at all traditional and not especially French, but is quite popular is chocolate strawberry turnover, and if you use French strawberries that makes it a bit more authentic!