She uses her own wedding as an example: "My husband is an only child of only child parents," she says. "So on my side we had 250 or 300 people, and his side he had eight!"

Nia Vardalos stars in My Big Fat Greek Wedding 2

She says that having all of these people in her life gives her plenty of material to work with. Even so, it took more than a decade to get to work on the sequel. "A few folks will claim I ran out of money or just wanted to kiss John Corbett again," she jokes, before making a serious admission. "Actually, it was a sad situation in which I was hiding that I was trying to become a mom. And it was really difficult for me. I didn't want to write about being a mother when I couldn't be a mother." 

All of this changed when she and her actor husband Ian Gomez (Cougar Town) adopted a 3-year-old girl through a foster care programme, a process she documented in her book Instant Mom.

For the sequel, she was determined that Ian (Corbett) and her character Toula would still be together ("Audiences don't want to see us divorced"), so she worked into the plot the idea that the spark has gone out of their marriage. This allowed Vardalos to look like a real over-worked mum in the film, appearing without makeup and wearing baggy sweats "like all mothers look when we drop off our kids at school and haven't had time for a shower".

And she thinks it's important that women get more involved in making movies. "Nobody's going to tell our stories for us, so we have to tell them," she says. "People say I'm a 'female screenwriter', and I say, 'My vagina didn't write my screenplays, I'm a screenwriter.' I try to be pro-woman without being anti-man, and I hope and wish that men could do the same in that when they look at the screenplay they say, 'Wait, is my daughter represented here, is my wife and sister represented?'"

And with so many stories to tell, she's already thinking that a third Big Fat Greek Wedding could be on the cards. "An idea came to me while making the second," she says evasively. "I haven't started writing, but discussions have started and I've had the offer."

Watch the trailer for My Big Fat Greek Wedding 2: