August 11, 2021 | 11:35am

This Easter egg is solid gold.

In the latest episode of HBO Max’s “Gossip Girl” reboot, Serena van der Woodsen’s wedding dress makes a glamorous reappearance.

Blake Lively’s character wore the sweeping gold strapless Georges Chakra Couture ball gown in the original series’ 2012 finale, which fast-forwarded to show her tying the knot with Dan Humphrey (Penn Badgley).

Meanwhile, this week’s episode of the new “Gossip Girl” is set during Halloween, with its key players attending a “New York legends”-themed costume party — and two characters dressing up as the original Upper East Side queens, S and B.

“Originally in the script, it was just written that they were wearing two of Serena and Blair’s most iconic looks,” costume designer Eric Daman, the mastermind behind “Gossip Girl” wardrobes both past and present, told Vogue.

Eric Daman, the costume designer on the original
Eric Daman, the costume designer on the original “Gossip Girl” as well as the reboot, posted this collage of the fashion flashback on Instagram.

“So that was something that we worked with Josh [Safran, the show’s creator], to figure out like what would be the most iconic moments for us to recreate.”

The throwback looks pop up on Pippa and Bianca, two girls from Constance Billard’s rival private school — and while Daman and his team remade Blair Waldorf’s cotillion gown for Pippa (Ella Rubin), Bianca (Katherine Reis) donned the exact dress worn by Lively almost a decade ago.

A closer look at Serena's gold Georges Chakra Couture wedding dress, as seen on the brand's Spring 2011 runway.
A closer look at Serena’s gold Georges Chakra Couture wedding dress, as seen on the brand’s Spring 2011 runway.
Georges Chakra

“It was so cool to see that brought back to life again, but in this new way,” Daman said.

Meanwhile, main characters Julien (Jordan Alexander) and Zoya (Whitney Peak) show up dressed as Beyoncé and Solange Knowles at the 2014 Met Gala, pre-elevator showdown; Daman created their looks from scratch as well.

When the half-sisters’ costume concept is leaked, however, Julien and Zoya ditch their red carpet-ready looks in favor of simple suits, channeling the Dan and Chuck to their nemeses’ Serena and Blair — and bringing the fashion flashback full circle.