Once in a while a truly original voice comes along. Paola Cortellesi's is such a voice. Once in a veryrare while a film arrives that transforms the way a nation views itself, shifts the terrain of public debate, and sends tremors through the body politic. Her bold, beautiful debut There's Still Tomorrow is just such a film. The story of its reception alone is fascinating. It is unsurprising that, in our mercantile societies gone mad on money, reviewers have focused on the film's runaway box office success. Granted, it is striking that There's Still Tomorrow 'outperformed' Barbie in Italian cinemas; not least because Warner Brothers spent more on marketing the former ($150 million) than it did on its production ($145 million), while the latter was made and marketed for a relatively modest $5 million – yet still stands as one of the highest-grossing films in a country with a history of world-class popular cinema. That is, though, one of the least interesting things about Cortellesi's phenomenal film.

More remarkably, it intensified Italy's soul-searching debate about domestic violence, hereditary misogyny and Italian machismo and became the focal point around which mass protests against femicide coalesced. There's Still Tomorrow had only been out a fortnight when 22 year-old Giulia Cecchettin was murdered by her ex-boyfriend – by which point last year over 100 women had already been murdered, which is to say one woman every 72 hours. The film struck a deep chord with women and girls, but also with a nation desperate to regain its moral compass and sense of civic integrity. From the 'historic compromise' and 'years of lead' through to the fetid corruption, debauchery and amplified sexism of the Berlusconi era, it's been hard for Italians not to look away in disgust. Cortellesi's sassy, soulful, delightful film might even have enabled Italy to recover its sense of identity and look itself in the eye once more.

The most astonishing aspect of all this is that those reactions and invigorating putative transformations will have been achieved not by a big-budget crowd-pleasing entertainment but, rather, by the inspired debut feature of a fearless 50 year-old woman who both directs and stars in a film glowing with heated humour and humanity but chilled by the darkness at the heart of Italian life. Imagine if Terence Davies' Distant Voices, Still Lives had captured the hearts and minds of the British public and packed community centres, film society screenings, fleapits and multiplexes across the land – as Barbie did and There's Still Tomorrow continues to do (not least in the Britain, where the film is being screened by the Vue chain). That it is impossible to imagine that says much about the relative intensity of the relationship the British and Italians have with their respective national cinemas.

Part of the popular appeal of Cortellesi's film to the several million Italians who have flocked to see it is not only its defiant laughter and sentimental sensitivities but also its implicit valorisation of the founding of the Republic and evocation of liberation after nearly three years of Nazi occupation, five years of war and 20-odd years of Fascism. Cortellesi has not only revivified the fortunes of embattled cinemas, generated debate and fortified resistance, as Greta Gerwig did, she has also revived memories of the golden age of Italian cinema with its echoes of the victory of the best of Italy. To achieve even half of the above-mentioned feats a film would have to be good, very good, but it would also have to reach a popular audience ensnared by television and the internet. That Cortellesi so spectacularly succeeds in that also says much about the affection Italians feel for their national film culture and their justifiable pride in it.

Earthed in neo-realism but tinged with magic realism and daringly hybrid, There's Still Tomorrow melds the hard-knock humour and surrealist invention of De Sica's Miracle in Milan and Rossellini's The Machine That Kills Bad People. It also combines the political purpose of Elio Petri's The Working Class Goes to Heaven and the Taviani Brothers' Padre Padrone. Cortellesi echoes the high water marks of Italian cinema while channelling Ana Magnani's imperishable performances in Pasolini's Mama Roma and Rossellini's Rome, Open City. In certain lights, Paola Cortellesi bears a striking resemblance to Claudia Cardinale at the same age. In There's Still Tomorrow, she plays herself playing Magnani playing Delia – a careworn but resourceful working-class woman successfully making a small budget go a long way while contending with the myriad depredations of patriarchy.

Cortellesi's extraordinary against-all-odds achievement – as a woman in a patriarchal society, a fledgling filmmaker in a male-dominated industry and a feminist role model – is built on a stack of mirroring processes. She embodies a series of entwined and layered realities: her own struggles are mirrored in the character she plays, who in turn mirrors the violence done and still being done to Italian women, which mirrors the violence of a system and society in which nearly two million families and six million individuals live below the poverty line, which is mirrored in the poverty implied by Cortellesi's homage to neo-realism.

In the epigram cited above, Godard continues, 'There is one strange thing however: how did Italian cinema become so great - when no-one, from Rossellini to Visconti, from Antonioni to Fellini, ever recorded sound at the same time as the images? There's only one answer: the language of Ovid and Virgil, of Dante and Leopardi had permeated the images.' I doubt Cortellesi would go that far. She might, though, say that the language of the streets, of what used to be called 'Il Popolo/The People', permeated the images of neo-realism which are resplendent and playfully subverted in her film.

As the film begins, Delia and Ivano Santucci (a chilling Valerio Mastandrea) stir from their slumbers. Almost before he's wiped the sleep from his eyes, Ivano lashes out at his wife. She receives this unprovoked assault unflinchingly, as a familiar feature of another day of fear and subjugation. There follows an expertly executed one-take slow-motion tracking shot in which Delia strides purposefully down the street, passing bicycle thieves and flower sellers, flirtatious G.I.s and wolf-whistling one-legged partisans, to the accompaniment of a deliciously funky-punky-blues from the Jon Spencer Blues Explosion. The message is clear: battered and bruised Delia may be, beaten she sure as hell ain't, and you better believe it. That scintillating sequence sets the scene too: we're in the war-ravaged Rome of 1946, not so far from the Naples described by Norman Lewis and Curzio Malaparte – where some sold themselves for a bar of chocolate and others sold their compatriots cheaply to the enemy.

As the film gathers pace we gradually discover more about the menial piecemeal jobs Delia does to feed her family, and more about the assaults upon her body and dignity inflicted by her brutish husband and his equally odious father, Otterino (Giorgio Colangeli), a bed-ridden patriarch at whose expense much fun is had. In the hands of a male director Otterino might've been presented as a 'loveable rogue'. Cortellesi doesn't let him of the hook. If father and son are cartoon baddies, so much the better as it is delicious to see such men diminished and caricatured for a change while strong, witty women dominate the screen. If father and son are cartoon baddies, so much the better as it is delicious to see such men diminished and caricatured for a change while strong, witty women dominate the screen. Delia is determined to save her daughter, Marcella (Romana Maggiora Vergano), from her own fate and will do so by any means necessary.

Those hints at romance aside, it is women who furnish the film with its most magical and memorable moments. The fragile solidarity of sisterhood is shared by the women who peel vegetables and gossip together in the square. They know what happens to Delia behind closed doors, when the shutters are shut. So does Delia's best friend, Marissa (Emanuela Fanelli), who shares food from her market stall and cigarettes she's tricked out of gullible American troops. Elsewhere, money matters. In her job repairing umbrellas, Delia is paid less than the idiot boy she's asked to train ('Because the kid's a man'). Button bright Marcella is refused access to education because she doesn't have the cash, while her unruly, perpetually squabbling and hideously entitled brothers are nurtured. Cortellesi eschews didacticism but reminds us of the continuing crimes against humanity of gender inequality and unequal pay.

When Marcella is courted by Julio (Francesco Centoramea), a handsome son of the bourgeoisie, money again raises its ugly head. Marcella squirms in embarrassment when Julio's well-heeled family are invited to dinner. What will they make of her mother's worn-out clothes, of her heretical grandad and foul-mouthed kid brothers? What horrors might unfold if Dad has too much wine? Delia's solution to this problem is to bribe the boys to behave and lock grandad up. It's the 'madwoman in the attic' of legend put joyfully into reverse. A message delivered not from the pulpit but from the comedy circuit (Cortellesi's huge popularity as a sketch show comedienne and 'national treasure' is another ingredient in the film's commercial success).

There's Still Tomorrow simultaneously indulges Italians in and denies them the easy comforts of nostalgia. This tug of war between hard realities and the pleasure principle plays out on Lele Marchitelli's pitch-perfect soundtrack. While the general tone is set with Italian retro and Eurovision pop (Mina's Nessuno, Fiorella Bini's rendition of Franca Mondi's 1956 hit Aprite le finestre), edgier and earthier sounds (Jon Spencer Blues Explosions's Calvin, Outkast's Bombs Over Baghdad) anchor the film in the contemporary. Davide Leone's flawless cinematography operates this way too: his nostalgic black and white nods to neorealism dovetail to telling effect with 360-degree revolutions and jump cuts. Cortellesi continually reminds us that women are disparaged, subjugated, violated and murdered now, as they were back then in post-war Italy.

Her acuity is writ large, too, in the way she handles the violence done to Delia. From the slap at the start of the film to a no less startling jazz dance in which husband and wife circle each other in a habitual ritual of brutality, she constantly surprises us. Forget Barbie and La La Land, forget the obvious, Cortellesi's moves are more audacious. That brilliantly choreographed dance sequence unanchors us in same ways the sudden dance scenes in, say, Samuel Maoz's Foxtrot and Nani Moretti's Aprile do.  Nowhere is Cortellesi's command of a medium familiar to her from 20-odd film appearances more evident than than in the film's breathtaking, deeply moving climax, about which, enough said.

A couple of years ago, I stumbled on an exhibition called Vita Nuova: New Challenges For Art in Italy 1960-1975. It presented snapshots of an extraordinarily fecund period in Italian culture during which cinema and literature, the ideas of the Left and the Women's Movement permeated gallery practices. Despite the dazzling images on display, it was a side-panel caption that stopped me in my tracks. It detailed various aspects of the subjugation of Italian women: they only gained the franchise in 1946, divorce only became legal for them in 1970 and, most shocking of all, they could be incarcerated for infidelity until as recently as 1981. Yep, until 1981 Italian men could kill their wives for 'betrayal' with impunity. All of which is to say that There's Always Tomorrow is a vitally important film that demands change, NOW!, while offering hope in a cynical age.

The film is imperfect, of course, as most directorial debuts are. Its visual gags occasionally feel forced, and sometimes Cortellesi strains too hard for sentimental effect. It proceeds in a series of vignettes, so it occasionally feels uneven. There's fun to be had in dissecting and dissembling flawed films, but, here, it's a pleasure to purr over the cream of film culture. Here, we count ourselves blessed to find a far-sighted, fragmented but coherent tour de force that growls with mischievous wit and political perspicacity. In There's Always Tomorrow, Cortellesi effortlessly pulls off the kind of high-wire walk most often associated with the most inventive and unsettling of humour: we gaze nervously upward toward the big top, tremulously aware of the risk and bravado embodied in the artist's every move, and then exhale and laugh with delighted relief when the lofty act has been safely executed. Like all true humorists, Cortellesi is so astonishingly sure-footed that she even throws in occasional missteps that draw gasps of recognition at the danger she courts.

That arch humorist J.B. Priestly maintained that true humour must keep its feet firmly on the ground, as Paola Cortellesi does. 'The contact with reality is important,' he says,  because 'the true humorist may indulge (herself) with some wild inventions but (she) never takes us up into the air to leave us there. Humour comes from our common life on this earth, out of the interplay of our characters down here.' Besides a healthy dash of reality, Priestley felt that true humour, as distinct from what is merely laughable, must contain elements of irony, a sense of the absurd, and some human affection. I'd add that it must also be fearless or it risks falling far and flat.