I believe that the best passage for you to excerpt for your purpose is the episode in which the narrator is given a petite madeleine dipped in a cup of tea by his aunt and the taste of the cookie brings back a host of memories. Unfortunately, I don't have a copy of Swann's Way handy, but the complete text is available online. I have copied just the reference to the work and the first few sentences. The entire episode covers several pages of beautiful writing. I don't know how long an excerpt you intend to use, but it would be nice if you could quote the entire passage, especially since it is so essential to understanding the whole of Remembrance of Things Past. You can Google the entire passage online by typing in petite madeleine and Proust. It was this experience with the petite madeleine (a scallop-shaped cookie) that the narrator tells us led to his writing the entire novel. It set him off in quest of temps perdu (lost time) which he recaptured in the final volume, The Past Recaptured.
Many years had elapsed during which nothing of Combray, save what was comprised in the theatre and the drama of my going to bed there, had any existence for me, when one day in winter, on my return home, my mother, seeing that I was cold, offered me some tea, a thing I did not ordinarily take. I declined at first, and then, for no particular reason, changed my mind. She sent for one of those squat, plump little cakes called "petites madeleines," which look as though they had been moulded in the fluted valve of a scallop shell.