Gala mashups are an opera-house staple, celebrating stars at the zenith of their bankability. Take opening night at the Met in 1994, an ad hoc double bill that pitted Plácido Domingo in Puccini’s Il Tabarro against Luciano Pavarotti in Pagliacci, with the 50-something Teresa Stratas as leading lady to both.

Flash forward to this spring, when the Finnish soprano Karita Mattila, 61, pulled off a more schismatic double-header than Stratas ever did, raising the curtain in Francis Poulenc’s grueling one-woman opera La Voix Humaine, then returning in her own Vegas-ready act with nary a guest star in sight. Captured live at the Finnish National Opera in Helsinki, Koko Karita is a total knockout.

Larger than life at a statuesque five-foot-ten plus stilettos, Mattila hails from the backwoods of southwestern Finland. She broke out early, conquering London, New York, and Paris in critic-proof Mozart, Wagner, Verdi, Strauss, and Janáček. But from the very beginning, her sensibility has skewed even more eclectic than that. For fun, back home in Finland, she would kick up her heels in vintage hand-me-downs from Marlene Dietrich, Marilyn Monroe, Judy Garland, and Liza Minelli. Koko Karita—­in drab English, Total Karita—puts the whole package together. If you think you hate crossover, Mattila just might change your mind. But is it still crossover when a star owns all she touches?

In Poulenc’s 60-minute emotional rollercoaster, Mattila appears as Elle, a discarded mistress, alone in her tony love nest, hovering by the phone for one last call from her ex, who, when he does ring, can’t wait to hang up. Letting her years show, Mattila neither glamorizes nor exaggerates Elle’s anguish. She sings the score beautifully yet without affectation, inflecting the prose of Jean Cocteau’s text as naturally as speech. Adding to the challenge, Jussi Nikkilä’s classy production fills in backstory with silent film noir clips involving Elle, her lying lover, and the mutual friend in line to be his next amour. And what do you know? Face to face with the movie cameras, Mattila rivals the stars of Ingmar Bergman.

Quick-change artist: Like a Vegas headliner, Mattila models lots of glamorous personae.

Reborn for the razzmatazz second half, Mattila dresses to kill in a half-dozen drop-dead outfits, hair and makeup styled to a fare-thee-well. Her song list leads off with “Mein Herr,” a showstopper Kander and Ebb added to the score of Cabaret for the movie; if Mattila’s rendition is airier and more amused than Liza Minelli’s, the “fine affair” the lyric commemorates is just as over. Marlene Dietrich’s Blue Angel signature tune “Falling In Love Again” (in German) gets a radiant new spin that may give you the shivers.

At that, the Finnish firecracker is just revving her engines. “With One Look,” Norma Desmond’s delusional Song of Herself from Andrew Lloyd Webber’s Sunset Boulevard, catalogues the powers of expression this washed-up sacred monster of the silents no longer possesses. Beaming with joyous intensity, stabbing the air with a scarlet fingernail, Mattila gives Desmond’s every cliché the sterling ring of truth.

“You can’t write that down!” declares the diva at the bridge of the song. No, Karita, you can’t. We won’t even try.

Koko Karita is available for streaming on the Ooppera Baletti Web site

Matthew Gurewitsch writes about opera and classical music for AIR MAIL. He lives in Hawaii