So Swann eats the madeleine and he’s off to the races: Memories, childhood and adolescence, flood the narrator and we have on our hands a long, tangled story that ends marvelously with the view that marrying Odette was a shock because she wasn’t even his type. The reader shares the breathless surprise. It’s fiction at its best because the reader has come to imagine the events as so real as to be shaken by them.
Nowadays, eating a madeleine and finding memories evoked seems on a pragmatic basis to be a slipshod exercise in pointless nostalgia. Why care about the past to the point that it serves any other purpose other than art? If the past is to be considered, that is, it ought to serve a function, and that function must be artistic creativity.
So when eating a madeleine I don’t think of earlier times: rather I consider its ingredients, why they were chosen, what they tell me about the origin of the cookie, what their percentages are in the cookie, who made the cookie, and how long cookies like it have been manufactured.
You can keep the past for all I care. Don’t look back.