So the story goes like this.

You are a cult writer/director who has just wrapped shooting your biggest project to date (and as it turns out, though you don't know it yet, one of the most successful movies of all time). You'll start editing the film – let's call it Avengers Assemble, shall we? – in a few weeks, but before you get to that you've got a week's vacation lined up. So what do you do?

Do you 1) sweep up wife and kids and fly to Europe to relax a little? 2) bunker down on the sofa, drink a few brews and watch the football (the American variety presumably)? Or 3) go home, yes, but then invite all your actor friends around to your house and shoot a zero-budget adaptation of a Shakespeare comedy, and write the music for it while you're at it. All in a week, the two weekends either side of it and one extra weekend a bit later.

Joss Whedon – the man behind Buffy, Firefly and Dollhouse; the writer who gave us Toy Story and a fair few episodes of Roseanne; currently one of the hottest directors in America after the success of the aforementioned Avengers Assemble (and, as you read this, a man busy beavering away on the sequel) – is the holidaymaker in question. And as you may have guessed by now, he chose option three, shooting a film in 12 days at his house with his mates for very little money.

It sounds like the kind of half-serious home movie idea best left to gather glitches on the computer hard-drive. Instead, Whedon's two-hour, black-and-white take on Shakespeare's Much Ado About Nothing, starring Whedon regulars Amy Acker and Alexis Denisof, has been travelling the festival circuit and is now about to close Glasgow Film Festival. I guess that qualifies it as the Hollywood version of a busman's holiday.

"It's workaholism at its most blatant," Whedon admits early on a sunny Californian Saturday. "But at the same time, it's literally the best vacation I've ever taken. And the most relaxed I've ever been on. And I came back to the Avengers in such a better frame to edit it having done that."

Whedon is at home this morning. He'll spend the rest of the day playing with his kids. But for the moment he's talking to me about no-budget movie-making, gender politics and corporate power.

We'll try to get to all of that. But it's only right to begin with the Bard. It turns out domestic Shakespeare has long been a Whedon trope, and the secret origin of Whedon's Much Ado actually goes back a fair bit. "It starts originally with my mother and my father who would have play readings at Thanksgiving and, as often as not, Shakespeare. And then me and some of my cronies at Buffy decided 'let's do this ourselves' and it became this little obsession."

This started around Buffy series five. The likes of Anthony Head and James Marsters would come over to Whedon's house and they'd all read Shakespeare's plays. "And at one point we did Much Ado, and Amy and Alexis read the leads, and I thought, 'if I'm ever going to film one of these things, it's gotta be these two'."

It helped too that the play is all set in one house. Whedon's own fitted the bill. It keeps the costs down. What was the budget anyway? "I can't put a figure on it, but whatever you're thinking, it's probably a little less."

Shakespeare's romantic comedy could, given its verbal battle of the sexes between Beatrice and Benedick, be the ur-text for Hollywood screwball comedy (in some parallel universe Cary Grant and Barbara Stanwyck will surely have filmed a version), but Whedon decided to film it because of the darkness he saw at its heart.

"When I looked at it really thinking 'OK, if I was going to film this, what would I want to say?', I [realised] everything that's happening in this is a lie. Everything is manipulation. Everything good and everything bad happens for the exact same reason – because some people got together and decided to tweak some other people."

Whedon believes that at the core of Much Ado is the idea that romantic love – the love that songs and films and plays regularly promote, the love of Much Ado's younger lovers Claudio and Hero – is actually a construct. More than that, real love, the play suggests, is something else. "The only way to real mature love is to get past the tropes of what we consider romance," Whedon suggests. "That to me was something very dark but kind of beautiful, and once I understood the darkness of the thing, and once I understood that Claudio and Hero's story is a real parallel to Beatrice and Benedick and they're not just filler, then I started to get more and more interested in it. And everything started to fall into place."

There's a challenge, though, that faces everyone who opts to adapt Shakespeare. How do you visualise a writer whose art is in the language? "The language is music. It's where the heart of the thing is, and knowing that I did have a very limited span in which to shoot it, I didn't spend an enormous amount of time trying to gild that lily. I just said 'here's the text and there's also a couple of musical numbers, but they're also in the text so don't blame me'. You just try to arrange the right place and the right energy to let the words happen and get out of the way."

Clearly Much Ado is a departure for Whedon, but there are still some clear links between what is in effect a zero-budget literary adaptation and Whedon's more typical high-concept, high-budget entertainments. There is his love of ensembles for a start (Whedon clearly adores actors). And then there's his fascination with gender issues. "It's always been an obsession of mine," he admits. Not much of a revelation given his interest in giving us female heroines.

The key deception in Much Ado sees Claudio led to believe that his betrothed Hero may have betrayed him. "Some people have given the text flak because they're like 'well, the whole text rests on whether Hero is a virgin'. And I'm like 'no, it doesn't. The whole thing rests on whether she's cheating on her fiance. The whole thing rests on whether he's being made a fool and she's having sex with someone else the night before her wedding. That's just about betrayal and heartbreak. It's not about whether she's, as the Victorians might say, intact. I find it strange when people can't get past the things that are clearly of another era to the reason why we are still putting on his plays."

Watching Much Ado, what's clear is that this film is also another of Whedon's classic investigations of power and powerlessness (filtered through Shakespeare, who had more than a passing interest in the same themes, of course.) It is also, as the first fruit of Whedon's new film company Bellwether, formed with his wife Kai, an example of a creator seizing the reins of power. Joss, is this your own superhero story?

"Yeah, to an extent it really is. I tend to write about people who are helpless or out of control who then regain or retake control, and I also tend to write a lot about big corporations. Now, I work for Marvel, which is owned by Disney. I worked for Fox for many years. I've worked for big corporations for a long time. No writer who works for a network or studio doesn't feel a little grouchy and a little helpless." With Bellwether he's decided to address that.

He explains: "It started with the [writers'] strike and the realisation that not only can we do these things ourselves, but that we have to. I'm very happy at Marvel and I'm having the time of my life working on Avengers 2, but at the same time you need this other outlet. And everybody has it. Nobody can't do what we did. It's absurd what technology has given us just in the last decade and not to take advantage of that feels like a waste of time.

"We're completing In Your Eyes, which Brin Hill directed from an old script of mine, which again is a left-of-centre, low-budget thing. Now we're playing with models about how to get that out to people. Just to be able to ask that question instead of asking 'When's our release date, please?' and 'Did our show get picked up?' and 'Is the corporation happy?' We're the corporation and we're definitely happy. We're happy people."

So there you go. This is a story about power and control and satisfaction. Mostly.

"Bellwether started basically when Kai turned to me and said 'I need you to make more cool things for me to watch'." Joss Whedon is doing his best to make that happen.

Much Ado About Nothing closes the Glasgow Film Festival on February 24 with Joss Whedon in attendance. It is due for UK cinema release on June 14