The celebrity chef prepared a seasonal menu for the crowd, which included Duchess Catherine, Rob Lowe, Rosario Dawson and many more celebrities.
To start, VIP guests enjoyed gorgonzola, tomato and basil pizzettes; pea pesto crostini; crispy smoked mozzarella with fig; salmon cakes with yogurt sauce; beef tenderloin crostini with curry mayonnaise; and chicken meatballs.
De Laurentiis also prepared a California chopped salad with Parmesan and marinated shrimp, which Kate ate as she chatted with the president of Tiffany & Co. and sipped white wine, as well as individual sweet corn lasagnas with blistered tomatoes and roasted asparagus.
Sporting a Victoria Beckham dress at the event, De Laurentiis told PEOPLE she wasn't given any dietary restrictions as she planned her menu, and was also told that Kate is an adventurous eater and that William likes to cook.
As for the food, she described it as "California cuisine with her Italian twist."
In weeks leading up to the polo match, the chef also admitted to being star-struck and said she prepared "a few special desserts that [the royals will] really love."
Her sweet choices?
A strawberry-meringue trifle; a tarragon-merlot truffle and a toffee truffle, as well as oatmeal, cranberry and chocolate chunk cookies; lemon ricotta cookies and more.
The waiter who served Will and Kate their salad course said the two were polite and friendly.
British ClassicAfter their polo match, the pair dressed up for the black-tie BAFTA Brits to Watch event – where their streak of good eating continued.
The star-heavy crowd enjoyed a filet of beef with creamed leeks for dinner, along with pickled garlic, asparagus, turnip, baby onions, potato fondant and a red wine sauce.
And the meal ended in a very English fashion: with a version of Eton Mess, a traditional dessert featuring rose meringue, strawberries, cream, sugar-dusted edible rose petals and pulled sugar.
A Final Send OffAn intimate Sunday morning event was held at the home of film producer/philanthropist Steve Tisch. The Tusk USA, an organization dedicated to preserving Africa's heritage and culture, brunch for 40 guests (including Reese Witherspoon, Catherine Keener and Linda Evangelista) was catered by Wolfgang Puck.
And while guests enjoyed Dom Perginon and noshed on passed hors d'oeuvres of eggs and salmon, tomato and burrata and other light salads, William and Kate spent their time making separate rounds and engaging everyone in attendance.
Before heading off, the pair also stopped by Sony Studios in Culver City, Calif., for the ServiceNation: Mission Serve veterans event with, yep, even more food.
The Duke and Duchess of Cambridge met with about 70 people at the VIP reception inside the Sony commissary, where guests nibbled on tuna tartare, figs with bruschetta and fried oysters.
After working his way through the reception line, Prince William, who was empty-handed, was rewarded not with a cocktail – but with a simple glass of water.
With reporting by LORENZO BENET, LIZA HAMM, MIA MCNIECE and SIMON PERRY