On a sunny Sunday afternoon, dozens of cookie lovers descended on the Upper West Side of Manhattan. They crowded into a small Crumbl storefront, which looked like an Apple store but smelled of Funfetti. They placed their orders on white tablets and snapped photos of their millennial-pink boxes of cookies.
Down the street at the original location of Levain Bakery, arguably the most famous cookie purveyor in New York, there was, astonishingly,…