The Sin City star admitted that she had an instant connection with the film producer after they met on the set of Fantastic Four in 2004.
"I just knew when I met him that I was going to know him forever. It was weird; he instantly felt like family," the 31-year-old actress told US InStyle.
"I'd never felt like that with anyone. We got each other. We're kindred spirits," she added.
Following their "very, very, very short" run as friends, the pair began dating and eventually married in 2008.
They are parents to two daughters - four-year-old Honor Marie and Haven Garner, 16 months - and Jessica admitted that Cash is still as romantic as when they met.
"On a weekend Cash might say, 'Go get your nails done with a girlfriend. Haven is down for a nap and Honor and I will play. I know you work hard. You deserve some time for yourself'," she said.
"That, to me, is romantic. He's saying, 'You matter', and that I'm more than just the mother of the kids or the wife who goes out to events with him."