There’s something about Allen & Delancey that seems nocturnal. The room, even in the early hours, evokes jaded roués, furtive assignations, and the airless ennui of adultery. So the debut of a stylish late-night menu is apropos. Chef Neil Ferguson tells us that the community board extended the restaurant’s liquor license to 2 a.m. “Anything in that room is sexy,” Ferguson says. “This food, I think, is more for soaking up alcohol.” That may be, but the menu is more than a little exciting. There’s a braised lamb neck, rabbit croquettes, and even, in the dessert section, a milk sorbet served with hot cookies made to order. Late-night service begins at 11:20 p.m., Thursdays through Saturdays, starting tonight.