The couple, who are now parents to daughter Annabella, were in an on-off relationship for several years after meeting in 2012.
With Mollie, 36, a member of pop group The Saturdays and Stuart, 37, playing cricket, the athlete told how they both put their careers first in the early days of their romance.
They briefly split up and struggled to keep in touch before reuniting in 2018 and jetting off on a make or break trip to Paris.
Stuart was due to go on another tour of New Zealand and worried the distance would keep him and Mollie apart once more.
So the pair went to the French capital for a few days to decide whether they wanted to commit to the relationship.
In his book Broadly Speaking, Stuart writes: ‘It felt like we needed to have a couple of nights and some time together to make a call on whether we could make things work, so two days after I got back from New Zealand, despite being worried about the jet lag, we were on the train to Paris.
‘We walked around the streets, sat and drank coffee, everything we could do in London. But somewhere else.’
Stuart and Mollie got engaged on New Year’s Day 2021 and their daughter Annabella was born in November 2022.
Tragically, Mollie’s father Steve died of cancer less than two weeks after Annabella was born.
Stuart described it as an ‘unbelievably emotional’ time for Mollie but said she was glad her father got to meet his granddaughter before he passed.
The cricketer also told how Mollie influenced him to retire from the sport in July simply because he wanted to spend more time with her and their daughter.
He writes: ‘Perhaps subconsciously, the fact I had barely seen Mollie and Annabella for the two previous months swayed me. It definitely makes you miss home, having a little daughter who is changing every day.’
Mollie proudly supported Stuart after he finished his legendary career with a 2-2 Ashes series draw in July.
Following a 17-year career that has seen him become England’s second most prolific Test bowler overall, he will now join Sky Sports’ commentary team.
Congratulating him on Instagram, Mollie wrote: ‘What a moment @stuartbroad – your last test! My darling, you’ve brought joy to so many cricketing fans all over the world, and especially to your family.
‘We have loved every single minute of cheering you on and we’re so incredibly proud of you.
‘Watching you live out your dream has been something I will never forget. Annabella and I will be cheering you and the team on today, as always. We love you so much.’