On Thursday evening, Barneys New York celebrated Isabel Marant’s Spring 2015 collection with a relaxed cocktail party and dinner, where guests like Mamie Gummer and Lily Rabe were treated to burgers, fries and miniature ice cream cones and a window display created by the French sculptor Arnold Goron. The lighthearted evening perfectly reflected the easygoing, effortless style the French designer is known for bringing to every collection. “For me, it has to be a mix of different ideas that makes it special,” Marant explained before dinner. For her Spring 2015 “started from a tribal feeling, but I tried not to be too literal. For example, the pleated skirt came from the straw skirts certain tribes wear. The prints you see all over the place were also the points of view of painters from the ‘50s, like Antonio Tàpies, whom I’ve always admired." Get shopping.