Felix Klein almost singlehandedly represented all of modern mathematics at the 1893 World's Fair in Chicago. At about 44 years of age, he was the embodiment of Göttingen mathematics, and Göttingen was the centre of the mathematical universe, at least that's how Klein saw it.
Klein gave many talks on the past and future of mathematics while in the greater Chicago area that year. However, with all his talking about the interconnectedness of geometries and best teaching practices, Klein might have missed going over to the Palmer House Hotel and witnessing the true star of the show.
If there was a formula for optimizing chocolate cake, the solution would be brownies. Not only are brownies much easier to make (no worrying about sifting flour, separating dry and wet ingredients, or beating eggs until fluffy), they are also far more dense, chewy, chocolatey, and satisfying.
I have made good brownies that were mistaken for "the best chocolate cake" (while in Paris, mind you). And I have made mediocre brownies that were mistaken for "very nice chocolate cake"–so I think that proves the point, anecdotally at least.
To return to Klein, brownies were introduced at the Columbian Exposition at the behest of Bertha Palmer as a dessert suitable for ladies because similar to cake but handheld. The original apparently included apricot jam, which seems like gilding the lily. But this was in fact during the Gilded Age, and hence apropos.
If Klein never got to try a brownie, then he certainly missed out. If he had one in 1893, he's probably been craving another since. In either case (proof by cases), there's no time like the present to eat chocolate, sugar, and butter.
Like myself, Klein wrote on the history of geometry in the early nineteenth century. I owe him a great deal, since he's full of outlandish quotes that are quite delightful to correct and make me sound more knowledgable. In exchange for a brownie, I plied him for the insider scoop on late nineteenth century geometry. Klein was happy to oblige and proved himself as much a gossip in conversation as he is in his books. Unfortunately, I wont be able to include all the juicy details in my future research, as there's no way to properly cite casual conversations with the long deceased.
Klein likes to talk and everyone likes to eat brownies, so it was a rather pleasant afternoon. I sent him home with a few leftovers and the recipe. They travel well and lend themselves to International Congresses, conversions, and conversations.