Lone Scherfig‘s An Education, a coming-of-age period drama set in 1961 London, is the absolute shit — the best film of the Sundance Film Festival, a finely tuned and deeply engaging film by regular popcorn-watching standards, an award-calibre drama that will definitely be in contention at the end of the year, and a movie that has launched a genuine movie star in an old-fashioned and yet very new-fashioned sense — 23 year-old Carey Mulligan.

An Education star Carey Mulligan during post-screening q & a at the Egyptian — 1.18.09, 5:05 pm.

I know that special old-soul-mixed-with-youthful-effervescence quality that you see in very few actors and actresses over the years, and trust me, Mulligan has it. A wondrously true and satisfying film has broken out of the Sundance ’09 pack, and a brand-new actress with just the right face and just the right approach and precisely the right touch of sadness in the corners of her mouth has hit one out of the park.

If I was a buyer I would have left the theatre at the 45 minute mark and started offering whatever it takes. When a movie works this well you don’t need to see the whole thing. You want to see it all, of course, but you know five minutes in that it knows what it’s doing and is playing the tune with just the right pitch and calibration.

It helps greatly that An Education is a sublime coming-of-age piece that’s been directed with fine assurance by Scherfig (Italian for Beginners) and that it has a wonderfully tart and wise and natural-sounding script by Nick Hornby. And that it also has a perfect cast that includes Peter Sarsgaard, Dominic Cooper, Alfred Molina, Cara Seymour, Olivia Williams and Emma Thompson . But it all rests squarely on Mulligan’s shoulders, and she keeps it fully aloft for its 95 minute length.

Nick Hornby, Carey Mulligan, Lone Scherfig, Dominic Cooper after this afternoon’s screening of An Education at Park City’s Egyptian.

Within two or three minutes I knew I was watching someone extraordinary. Mulligan’s Jenny is a very bright and vivacious 16 year-old living a somewhat stifled, middle-class life and pinning her hopes on being admitted to Oxford University. She is spirited but not daffy, off-beautiful and clearly wise beyond her years. What’s extra-special about Mulligan is that she possesses — in this film, at least — a perky A-student Audrey Hepburn quality that makes you fall for her at the drop of a hat.

The odd thing is that An Education is set at a time when Ms. Hepburn’s career was going great guns, and it has a special made-in-the-60s quality — you’re thinking right away that John Schlesinger of 1965 or ’66 could have directed it, or Francois Truffaut — that is quite intoxicating. It sort of allows you think that you’re watching it in the ’60s, and that the very-new-to-the-scene Mulligan is about to knock Hepburn off her pedestal because she has the same kind of pluck but a lot more soul and melancholy in her eyes.

The story is about how Jenny, bored to years by her suburban existence, is instantly smitten by a much older but very urbane and amusing guy, David (Sarsgaard), in part because he brings so much in the way of excitement and sophistication into her life. A bit of a rascal and a con artist and yet a man of taste with a sense of real fun, David half-persuades but more often hoodwinks Jenny’s parents (Molina, Seymour) into letting him take her to this and that concert, art auction, grand party or late-night dinner with his two lah-lah friends, played by Cooper and Rosemund Pike.

David essentially becomes Jenny’s new teacher — her escort-guide into a glam but shady world whose true nature and agenda reveals itself only very gradually. But when it becomes clear…well, let’s spare the details for now but it’s a serious breath-taker. But our Jenny is no basket case waiting to crumble. The fact that she’s strong, bright and focused is one of the pleasures of her character. There’s never any worries on that score.

An Education, trust me, will be announced as a Fox Searchlight or Focus Features or Sony Pictures Classics acquisition within hours. Okay, by tomorrow.