If you’ve ever wondered how to love someone honestly and still laugh heartily at her follies, Stephen Temperley has your case study: His Souvenir, a “Fantasia on the Life of Florence Foster Jenkins,” celebrates that real-life society lady and her midcentury musical delusions—which led her, after years of semi-private recitals in a Manhattan hotel ballroom, to serenade a sellout Carnegie Hall crowd with her excruciatingly off-key attacks on the Matterhorns of the operatic soprano repertoire—with a gratifying mix of affection and appalled wonder. It’s delicious material, and Temperley handles it with much more delicacy than the legions of music-school undergrads who’ve kept the Foster Jenkins legend alive—and Serge Seiden’s joyful, mischievous, marvelous production at the Studio Theatre is an utter delight.

That’s due in no small part, of course, to the ideally cast Madame J: the singular, superlative, and possibly certifiable comedian Nancy Robinette, now marking her 29th season at Studio. Robinette has long been a Washington theater institution, the go-to actor for crazy ladies and comic gorgons and giddy old broads, whether they’re bustling through a Restoration Comedy parlor in period gowns or dithering about in a ratty rain slicker in some grubby modern kitchen.

But Robinette can also be a shattering dramatic actor (as anyone who saw 2006’s Frozen at Studio, or indeed 1996’s Obituary Bowl at Woolly Mammoth, can attest)—and when you watch her closely, the two types turn out to be tightly linked: At their core, her batty comic personas all share a trembling vulnerability, a real, intimate, convincing humanity that makes their foibles all the funnier and their little tragedies all the more poignant. Toward the end of Souvenir, when the heretofore fearless Madame J suspects for a moment that the transports of her delirious fans may have less of rapture than of ridicule about them, that vulnerability comes frighteningly, movingly, nakedly to the surface for a moment—and it’s downright heartbreaking.

On the brisk ascent to that pinnacle, Robinette delivers a finely calibrated performance that generates plenty of comedy without ever stooping to ask for the audience’s laughs. And J. Fred Shiffman—an epicene, ivory-tickling, cabaret-crooning delight as Cosme McMoon, the narrator-accompanist and budding composer who serves as undeceived acolyte at Madame J’s altar—sprinkles grace notes and glissandos of dry, conspiratorial hilarity throughout, at once inviting the audience to snicker and forbidding them to sneer. It’s a sly and deliciously subtle bit of showboating; you’d call it larcenous if the play weren’t really all about Cosme’s melancholy search for his place in New York’s musical landscape, anyway.

Seiden keeps his efficient, unsentimental production, which plays out around a vintage baby grand in a handsome hotel-parlor set by Luciana Stecconi, moving always toward the scene of Madame J’s next disaster—until suddenly, sadly, there aren’t any more to come. Like James Dean and Nick Drake, Gilda Radner and Selena, and princesses from Grace to Diana, Florence Foster Jenkins left this world before the bloom could come fully off her superbly idiosyncratic rose. Studio’s loving, laughing Souvenir makes it clear just how much she’s worth mourning.