The sun came out just as it had started to set across the far-eastern end of Long Island (it had rained all day). Gwyneth put on a yellow silk, abs-accentuating pj set from Olivia von Halle and layers of gold necklaces and bracelets from Cartier. And guests meandered toward a stunning private Amagansett shingled stone barn through a lush vegetable garden and orchard, past chicken coops and some particularly adorable chickens.

1. “Is everyone else really wearing pajamas, or am I the only one?” was the most common question as guests checked in, followed by “And what is Sleep Milk?” They were there to celebrate the launch of GOOPGLOW Dark Spot Exfoliating Sleep Milk and the recently opened seasonal Cartier boutique in East Hampton (goop and Cartier threw the intimate dinner together, and the invitation spelled out that both pj’s and Cartier were required attire); the silky, sun-damage-obliterating new serum had yet to be revealed.

2. 

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Trays of special Cartier champagne bottle flutes greeted the guests as they stepped inside, along with twinkling lights and flowers that streamed from the ceiling. “I wore my cat pajamas specifically for the one (GP) who hates cats the most,” said author Jessica Seinfeld. Caviar stations were stocked with ROE caviar, and a silk-pajama-clad band played violin and accordion. Created by event designer Mimi Brown, the party felt romantic and lighthearted—like a really, really glamorous sleepover.

The Sleep Milk mystery was solved as everyone sat down to dinner: At each place, on top of new, deep-blue goop x Social Studies china plates (coming this fall; watch this space) was a bottle for each guest. “Welcome to my midsummer night’s dream dinner,” said Gwyneth. “And now you know what Sleep Milk is—it’s my favorite product we’ve made yet. It really is beauty sleep in a bottle. Try it tonight and you’ll wake up in the morning and you won’t believe your skin.”

Dinner (the menu was printed on custom Cartier paper) started with a salad of summer vegetables, moving on to branzino al cartoccio and a local berry clafouti, with a special lavender sleep milk tonic for a nightcap. “Under the stars with the lovely Gwyneth Paltrow,” marveled broadcast journalist and attorney Savannah Guthrie. “Then straight home to bed to exfoliate like a good goop girl.”

“Good night—more like goop night, amirite?” said journalist Aly Weisman.