The Lacheys celebrate Simpson's new CD in Hollywood. Plus: Madonna, Heidi Klum, the Olsens and more

TOGETHER ... WHERE EVER

Ashley (right) and Mary-Kate Olsen hook up in Hollywood Thursday at a party for design house Tsubi at the Chateau Marmount. Mary-Kate took a leave of absence from her studies at NYU this semester to return to the West Coast and the twin moguls' billion-dollar company, Dualstar.