Overview: The biggest and baddest dessert chefs are joining us to celebrate our 16th season with a Sweet 16 party! First, "Cake Boss" Buddy Valastro surprises Rach with a rainbow shag cake masterpiece. Then, Milk Bar's Christina Tosi makes one of her favorite recipes: Apple Cider Doughnut Cake, layered with apple cider jam and cream cheese frosting (YUM). And "Top Chef's" Gail Simmons shares her Bumbleberry Pie Sundae recipe. Plus, Rachael's making a Japanese-inspired noodle bowl.