Christopher Kimball sets out to make his ultimate recipe for Buttermilk Biscuits. Bianca Borges bakes Browned Butter Gateau Magique, a French "magic cake" where the batter separates into three distinct layers. Wes Martin figures out how to make flavorful, easy-to-roll-out Iced Buttermilk Sugar Cookies. And Regula Ysewijn shares a history lesson on Christmas pudding.