Gypsy's Arm Cake Roll (Swiss Roll) vs Classic Black and White Cookie

Both desserts rely on eggs, milk, butter and sugar but put them to very different work. The Swiss roll whips eggs and sugar into a light, flexible sponge scented with lemon zest and vanilla, then rolls it around a silky pastry cream of milk, cornstarch and a cinnamon stick finished with butter, with jam as an optional alternative and powdered sugar dusted on top. The black and white cookie creams butter and sugar, lifts the dough with baking powder and milk, and turns powdered sugar into two smooth glazes, one vanilla and one cocoa, so every bite is split in flavor.