Ashlee's big sister, Jessica Simpson, and her hubby, Eric Johnson, also stepped out for the soiree. Jessica went for an ultra-sexy look for the party: a mini LBD with sheer paneling in the middle that showed off major cleavage.
Evan made it very clear that it was his wife's big day, showering her with plenty of PDA and stealing kisses throughout the night. (It is kind of his thing, after all.)
At the dinner, the tight-knit crew dined on kale and apple salad, oven-braised chicken meatballs and salad, but it was the Gucci-themed cake that Jessica presented to Ashlee that was the evening's sweetest treat. “She was over the moon!” an eyewitness told ET.
The festivities moved to a second location, Warwick, later in the night. They stayed at the Hollywood hot spot, co-owned by Sylvain Bitton, JT Torregiani and Eli Wehbe, until about 2 a.m, sipping cocktails and keeping a low profile. "Evan never left Ashlee’s side," an eyewitness tells ET. "She was snuggling up to her husband all night long.”
After the soiree, Ashlee took to Instagram to share how grateful she was to hang with her ride or dies. "Such a FUN birthday party this weekend @ beautyessexla ! Beautiful night with beautiful people ?," she wrote.
On her official birthday, Evan shared a very sweet throwback photo of the pair in all their bohemian glory.
"HAPPY BIRTHDAY!!!! To my BeAUTIFUL WIFE. Im so thankful for you every single day!!! I love you with all my heart!!!" he wrote on Instagram. "This picture is from one of the first trips we ever took together to CABO. I already new then I wanted to be with you forever! Im obsessed with you baby! Have the best day ever!"