This question serves two purposes. One, the interviewer is looking to see if you have researched their menu before your interview. Two, the interviewer is checking to see if you have the ability to upsell and romanticize the menu items enough to have a customer choose a dessert before asking for their bill.
"Your cannoli are to die for, so I would have no problem selling them to you. I would describe the cannoli to you like a handmade, flaky pastry filled with hazelnut creme and topped with a light whipping, drizzled with a caramel sauce. Mouthwatering."
"When presenting the dessert menu, I always say to my table, 'You can never leave dinner without something sweet.' It entices them to at least take a look and see if anything catches their eye. On the First Watch Restaurants, Inc. menu, your seasonal cheesecake has never let me down, so I would sell the cheesecake to you by describing its flavors and letting you know that it's as good as Grandma makes."