There are a number of exclusively Parisian pleasures, many of them seasonal, including les cèpes (boletus), of which there seems to be a goodly supply this year, though the prices are still through the roof. Luckily you can buy one or two or three, which is enough to make, or at least start a meal for two. I can think of few edibles more delicious, perhaps none, though I am inordinately fond of chocolate in any form, and cheese.
Once selected at the vegetable stand on the corner (an art in itself, choosing the best ones under the eye of the greengrocer who does not like customers handling the produce; unless you are a regular customer of that fruit and vegetable stall, you mustn't expect the grocer not to try and off-load the duds on you. Even if you are a regular customer, it is prudent to doublecheck her or his selection).
Carry them home gently, gently brush off the soil still clinging to the stalks and (in view of what you have paid for them) trim as little as possible. For some reason this makes me think of toenails (fungus associations?). Sorry. Heat a little good, sweet butter in a large pan, and when it is just beginning to froth, add the sliced mushrooms, or better, slice the mushrooms into it. Do not overcook! Salt, pepper. Consume immediately, with some good, darkish French bread, say the baguette called Paline from Kaiser on the rue Monge (with branches elsewhere, possibly now including New York).
I should also mention les pommes Reine de Reinettes, which have a short shelf life, like yellow transparents, and therefore are probably doomed to extinction as non-sustainable in a capitalist economy. Red and yellow streaked, they make great applesauce. If they don't melt quickly when you cook them, they have been doctored.
Should go back to the Potager du Roi in Versailles one of these days.