Behind a dark brown door, just around the corner from Bloomingdales on New York's chi-chi upper east side, hides a fairy grotto of sugary delights. From the outside it looks like the sort of place your grandmother would go shopping for ornaments. But unless her idea of desirable trinkets includes furry handcuffs, chocolate dog treats and saucily-sloganed fridge magnets, she'd be one disappointed lady.

This is sweet-shop-cum-restaurant-cum-tat-store Serendipity 3 – full of kitschy frippery and Tiffany lamps, and home to the Guinness World Record-winning most expensive desserts, the Golden Opulence Sundae and Frrrozen Haute Chocolate, costing $1,000 (£506) and $25,000 (£12,641) respectively. But that's not all it's been home to - in November, it was discovered to be providing free board to some unwanted visitors of the four- and six-legged variety, resulting in a temporary closure by the Department of Health.

Now reopened with a clean bill of health, the only things the place is crawling with are tourists looking for a slice of glamour — since it opened in 1954, star customers have included Cary Grant, Marilyn Monroe and Grace Kelly. It was also a meeting place for the fashion set in the 50s, and Andy Warhol was a regular visitor, paying his bill with drawings.

These days, Serendipity's website (worth a read for its sheer flamboyance) regularly updates its news page with gushing showbiz reports of the latest famous faces to visit, from Nicole Kidman and Cher to Lindsay Lohan and Spike Lee. But the film connection doesn't end there - the store has appeared in a number of mediocre girly rom-coms, including One Fine Day, Trust the Man, and most notably the widely-rubbished Serendipity. The latter has a wildly unconvincing plot, but its masterstroke is a scene where the love interests dine on Serendipity treats - if there's a more enticing combination than hot fudge sauce and John Cusack, I've yet to hear of it.

While the fear of finding the wrong kind of chocolate sprinkles in your sundae may affect Serendipity's popularity in the short-term, it's likely to bounce back. Having eaten there two days before it was closed down, I'd happily go back there and gobble another pudding tomorrow if given the opportunity.

The desserts, when they come, are the size of your head, served in mammoth glass dishes and covered in mountains of whipped cream and maple walnut topping. They have drool-inducing names like Chocolate Blackout Cake, Aunt Buba's Sand Tarts, Dark Double Devil Mousse and Cheese Cake Vesuvius.

But the real showstoppers are those that seem to divide opinion on whether they're appealing or appalling. The Golden Opulence sundae is a vast confection of sweetened caviar, gold leaf and Armagnac, served in a Baccarat Harcourt crystal goblet and topped off with a gilded sugar flower and 18-carat gold spoon. The Frrrozen Haute Chocolate offers a blend of 28 cocoas from around the world, is infused with 23-carat gold and La Madeline au Truffle from exclusive Knipschildt Chocolatier, and is served in an edible-gold-lined goblet with a gold and diamond bracelet.

For the regular working stiffs among us, a plain old Forbidden Broadway Sundae (Chocolate Blackout cake, ice cream and hot fudge topped with whipped cream for $13.50 (£7)) is the only sort of excessively rich dessert within reach. But that's more than rich enough for most people, and if Serendipity's little incident has taught us anything, it's that the one thing you really can't put a price on is good hygiene.

· Serendipity 3, 225 East 60th Street (between 2nd and 3rd Avenue), New York; serendipity3.com