In his long career on Wall Street, Mark Klein has scrupulously avoided mixing business and pleasure. But lately he cannot help himself. “We always bring cupcakes to our business meetings, and everybody has a smile on their face,” says Klein, 49, the former CEO of investment bank Ladenburg Thalman.

Think of it as market research. Klein’s 57th Street General Acquisition Corp., a special-purpose company, recently injected capital into Crumbs Bake Shop — the largest U.S.-based cupcake purveyor — to enable the 34-store chain to go public and expand to 200 locations by 2014. (The rumor that a newly activist SEC wanted to vet the deal because cupcakes are “derivatives” of cakes is false.)

Crumbs’ 82 percent, three-year compound annual growth rate could make this transaction as sweet for Klein and his investors as the cookies-and-cream cupcakes he likes so much. As to skeptics who say cupcakes are a fad, Klein retorts, “Cupcakes are well known, well respected and well liked.”