04/06/2009 at 04:00 PM EDT
Iron Man sure knows how to throw a birthday party! Robert Downey Jr., with wife Susan by his side, celebrated turning 44 Saturday night at Beverly Hills's Thompson Hotel, in their second level BondSt Beverly Hills Lounge.
The party of 75 guests included pals Sting and wife Trudie Styler, Gwyneth Paltrow
and Chris Martin, Reese Witherspoon
and Jake Gyllenhaal
, Ben Stiller and Christine Taylor, Jon Favreau and Sam Rockwell.
"Gwyneth and Jake talked for a while about an upcoming project," says a guest. And during the night, "Jake and Reese looked very in love. They were being super affectionate, holding hands as they sipped on glasses of wine. They laughed a lot!"
As for another hot A-list couple nibbling on BondSt sushi platters of spicy tuna, sesame crusted shrimp, and sun-dried tomato avocado rolls, says the source, "Gwyneth and Chris arrived and left together. And they looked very happy."
At the end of the evening, guests toasted with hot sake, while Downey Jr. sipped espresso. And, to cap off the festivities, guests satisfied their sweet tooth with BondSt's individual chocolate meltdown cake. "He was very touched," the source says of being serenaded with "Happy Birthday."