Britney Spears and her fiancÚ, Jason Trawick, are staying at the Mondrian SoHo for the week to enjoy a New York City Christmas vacation.

Wednesday, the newly engaged couple enjoyed a night out on the town for a girlfriend's birthday at the hot restaurant, The Derby.

Tucked into a private booth, Britney, sticking to water, enjoyed many of the West Village eatery's specialties, prepared by Chef Alex Guarnaschelli.

Possibly to make the special guest feel at home, Lady Rizo and The Darby band serenaded her with a cover song tribute of Britney's hit song, "Toxic." After dinner, the couple headed back to their hotel hand in hand.