Satire is always best (and usually only bearable) when it's sharp. When the insight is as dull-edged as it is in William Hamilton's new play White Chocolate at the Century Center, only a vivifying theatrical presence or some robust comic writing can prevent the show from devolving into arid, talky pabulum. Well, one out of two ain't bad.

One suspects that there's a solid play somewhere in Hamilton's concept, though the playwright hasn't yet figured out how best to unearth it. Taking on the institutional (and unintentional) racism of the upper classes is an idea with real possibilities, and the story's setup - a Boston Brahman, Brandon (Reg E. Cathey) and his New York Jewish wife Deborah (Lynn Whitfield) wake up one morning to find themselves black - suggest something that could easily brim with social insight.

But Hamilton is content with approaching the story as an upper-crust New York comedy along the lines of something George S. Kaufman might have penned in one of his off periods. Missing, though, are the sparkling dialogue and keen wit that Kaufman specialized in and gave the majority of his plays a real sense of specificity and character that belied their often humble plots. In the way Hamilton peppers his play with misunderstandings between Brandon and Deborah and their daughter Louise (Samantha Soule) and her fiancé Winston (Paul H. Juhn), he seems to be writing little more than a series of one-liners more appropriate for the cartoons he's spent 40 years supplying for The New Yorker.

Racial politics, at any level, are more complicated - and far more interesting - than this, so the characters' devil-may-care attitudes rob the play of any real dramatic power. Making Winston Chinese is clever, as is making Brandon one of two candidates for the directorship of the Metropolitan Museum of Art (the other is the black Ashley Brown, played by Erik Laray Harvey). Unfortunately, when these worlds collide, the results are never as funny, suspenseful, or even offensive as would be ideal to make any significant points about how all these groups interact in person and behind closed doors.

Hamilton spends much of the rest of the time dwelling on issues of mistaken identity: Deborah and Brandon are constantly assumed to be two black actors portraying the couple, though Winston actually believes they are Louise's real parents. These various misunderstandings do provide a modicum of amusement, though they never develop into anything that pays off for the audience beyond quick-fix laughter. For a play that purports to dissect and treat a topic of this degree of seriousness, however, it's not enough.

That's why Hamilton and director David Schweizer should thank their lucky stars for Julie Halston. The actress, who replaced the originally cast Nora Dunn, is the only person involved with the show capable of elevating it from the mires of at best moderate enjoyment into something infinitely more savory. Halston plays Brandon's sister, a woman who is trapped in an unhappy marriage and positively convinced of her own progressive attitude while displaying exactly the opposite, with a delightful low-class bent that smashes social strictures more successfully than anything else Hamilton has written here.

Rattling off her lines at high speed and with a symphonic sense of musicality, Halston is an unstoppable comic force here. Though she's a wonder throughout, even when the play lets her down with some foreseeable plot twists near the end of the second act, she's never better than when romping around the stage in blackface and braying in a thick Irish brogue near the end of the first act. More miraculous still, for the 15 or 20 minutes surrounding this unforgettable episode, White Chocolate descends to the deepest depths of absurdity - and flourishes there.

This sequence makes you realize all too clearly what's missing in the rest of White Chocolate: daring originality. The lead performers are all competent, and Cathey, Whitfield, Soule do make strong impressions; James Noone's black, white, and sepia-tinged deluxe townhouse set appeals greatly, as do David Zinn's elegant costumes; and Schweizer's direction, while often in the over-caffeinated style of a Kaufman revival, keeps you interested enough to make you feel you're watching a better show.

But when Halston is onstage, and when Hamilton really lets himself go, this actually is a better show. It's even almost a good one. But moments of concentrated brilliance like these can't completely sell the show the way Hamilton intended, and this fact - along with the lulls present throughout the rest of the production - don't make the evening a complete success.

Kaufman famously said, "Satire is what closes on Saturday night," but White Chocolate will likely run much longer than that - especially if Halston can keep up the energetic, exciting pace she's currently using to lead the way.

White Chocolate
Running Time: 2 hours, 10 minutes with one 15-minute intermission
Century Center for the Performing Arts, 111 East 15th Street
Tickets online and current Performance Schedule: Telecharge