Chiffon cakes are different than other cakes in that they're made with oil instead of butter. Also, like in these chiffon cupcakes, the eggs are separated into yolks and whites. For chiffon cakes, the whites are whipped to soft peaks. The whipped egg whites lighten the batter and help it rise. The egg yolks and the vegetable oil make chiffon cakes both tender and moist.