Courtesy Hsing Chen; AdMedia/Splash News Online

Being Giuliana Rancic means having your designer purse — and eating it, too.

On August 9, the E! host thought she was simply attending a meeting at RPM Steak, the soon-to-open Chicago restaurant (and sibling to RPM Italian) that she owns with husband Bill Rancic.

Turns out the reality star had planned an surprise party for his wife, who turns 40 on August 17, complete with a stunning Birkin-inspired cake by pastry chef Hsing Chen of H Patisserie.

“She was very surprised when it was brought out,” Chen tells PEOPLE. “She thought she was just having a meeting but this whole thing was planned ahead of time for her.”

Rancic posted her own shot of the cake with the caption, “Thank u for my gorg birthday cake @billrancic! I want to wear it!!!”

Why the handbag? “That was what Bill wanted her to have. The idea generated from him and my guess is that she just loves bags,” Chen says. It sounds like a reasonable theory, as the ultra-stylish host has spoken openly about her love for her own black Birkin and has often been spotted carrying the gorgeous arm candy.

The cake-imitates-purse theme is a recent trend in Giuliana’s life. Last week she also posted the below shot of a cake modeled after a Chanel handbag with coordinating cake pops, which was taken during yet another Bill-orchestrated surprise celebration with friends. (The group appears to have flown together to Chicago on a private jet, and the treats were brought by Giuliana’s “BFF,” author Colet Abedi.) “I don’t want to devour it, I wanna wear it!!!” she gushed in the caption.

According to Chen, the Birkin confection was not just for show: The devil’s food cake, which was layered with chocolate ganache, was served to the couple and the group of about 15 well-wishers. The chef says her masterpiece took about three days to complete.

“The hardest part was getting the exact shade of orange and making the hardware and stitching look realistic,” says Chen, who adds that although she worked from photos, “it would have been nice to have an actual bag handy for reference.”

—Lexi Dwyer