The best good news about “Here We Are,” the combo platter Buñuel musical that opened on Sunday at the Shed, nearly two years after Sondheim’s death in November 2021, is that it justifies the idea of merging these two works and succeeds in making a surrealist musical expressive. In Joe Mantello’s breathtakingly chic and shapely production, with a cast of can-you-top-this Broadway treasures, it is never less than a pleasure to watch as it confidently polishes and embraces its illogic. Musically, it's fully if a little skimpily Sondheim, and entirely worthy of his catalog. That it is also a bit cold, only occasionally moving in the way that song would ideally allow, may speak to the reason he had so much trouble writing it.