Ashton is well known for his tech-business ventures and, during the early stages of the couple's relationship, he shared some of his future financial plans with his girlfriend.
"Early into our dating, two things came up," Mila told America's "The Late Show" host Stephen Colbert. "He was like, 'Hey, there's this kind of company, it's kind of like a rideshare... it's like a cab company, but anyone can drive the cab.' "
Kunis thought her guy had lost his mind and told him, "That's the worst idea ever," adding, "I was like, 'You're going to put me in a car with a stranger? What is wrong with you?' Like, I was furious at him."
These days, the mum-of-two is much more savvy about the family's investments, which have produced huge pay-outs thanks to savvy stock picks like Airbnb, Spotify, glasses brand Warby Parker, and home design company Houzz.
"I am a big consumer," Mila explained. "I feel like I have really good gut instincts on consumer goods, and so, if it's coming out of our personal account, I do vet all the companies."
But the stunner admitted the Uber snafu wasn't her only rookie investor error in the early days of her romance with Kutcher.
"He sat me down and was like, 'Hey, I got to explain this to you, tell me if I'm crazy... there's this thing, it's like mining for money, it's called cryptocurrency; it's called Bitcoin,' " she remembered.
Once again, Mila turned her nose up, telling Ashton it was a "horrible idea" but the businessman responded, "Cool, we're investing in it!"
"This happens all the time," she added with a smile. "There's companies that he'll talk about that, to me, seem so ludicrous... and yet, here we are."