What’s tall, dark, and frosty? Colin Firth, for one. For another, there’s the frozen hot chocolate shared by sexy soul mates John Cusack and Kate Beckinsale in the romantic comedy Serendipity. In a scene that takes place at NYC’s cozy eatery Serendipity 3, the fate-crossed lovers are served the cold concoction — a menu staple since 1954. (Fans include Barbra Streisand and Cher.) ”Since the movie came out, there’s even more demand,” notes restaurant owner Stephen Bruce. You can try mixing up a batch of your own — the decadent drink is made of a blend of 14 imported chocolates mixed with milk and ice and topped with whipped cream. Better yet, order online (Bruce recently fielded 40 orders in one hour on serendipity3.com) or drop by the restaurant’s boutique, which offers a gift box ($20) containing two packets of the drink mix, straws, spoons, and a goblet. As for finding the love of your life, you’re on your own.