Kris Humphries and Kim Kardashian
05/25/2011 AT 12:45 PM EDT
05/25/2011 AT 08:00 AM EDT
It was a dream come true for Kim Kardashian
when she walked into her Beverly Hills home May 18. Her boyfriend of six months, New Jersey Nets forward Kris Humphries
, was waiting in her bedroom on bended knee with four words written in red rose petals: "WILL YOU MARRY ME?"
"I didn't expect this at all," Kardashian, 30, tells PEOPLE in an exclusive interview (out Friday) of the romantic, surprise proposal. "I was in such shock. I never thought it would happen at home, and I never thought now."
Humphries popped the question with a custom-designed, 20.5-carat Lorraine Schwartz diamond sparkler. "I just knew I wanted it to be big," says Humphries, 26, who, with the help of Kardashian's mom Kris Jenner, planned an intimate family celebration later that evening.
"Kris really didn't want a big celebration, but he had jokingly told my mom he'd be fine if there were mini-horses there," says Kardashian with a laugh. "Later that night at the party, my mom brought out two mini-horses, covered in glitter, for us! It was hysterical!"
For exclusive personal photos from Kim's engagement party – and all the details of her emotional proposal – pick up the new issue of PEOPLE, on newsstands Friday