Frrrozen Hot Chocolate. It seems like a contradiction at first, something that defies the laws of beverage physics. Yet it's that very drink that has long defined Serendipity 3, an Upper East Side dessert destination since 1954. In a business profile for New York magazine, Hal Rubenstein summed up his thoughts on the signature treat—"It's like riding the Cyclone and giving a hickey: You have to do it at least once in your life."

That frozen beverage, or "frrrozen" beverage as it's fittingly called here, complements a full lineup of desserts: apple pie, fresh fruit sundaes, and ice cream crepes just to name a few. Serendipity 3 even holds the Guinness World Record for the world's most expensive dessert. Their Golden Opulence Sundae covers rich Tahitian vanilla bean ice cream in 23-karat edible gold leaf and other rich and exotic ingredients. The dessert, which must be ordered 48 hours in advance, comes with a bill for $1,000.

The shop's setting echoes its whimsical menu. Stained glass Tiffany lampshades and funky decor—like a giant skeleton key that hangs from the ceiling—offset the whitewashed walls of a Manhattan townhouse. The location has seen its fair share of famous faces over the years, including President Bill Clinton, and regulars have passed decades enjoying country meatloaf and hamburgers topped with chili. Of course, Serendipity 3's desserts remain the star, and the shop sells many items for customers to take home, including hot chocolate mix and hot fudge sauce.