Jürgen used a 'chiffon sponge' as part of his showstopper for The Great British Baking Show ™ in Cake Week.

A chiffon cake is a very light cake made with vegetable oil, eggs, sugar, flour, baking powder, and flavorings. Being made with vegetable oil, instead of a traditional solid fat such as butter or shortening, it is easier to beat air into the batter. 

Chiffon cakes achieve a soft texture by having egg whites beaten separately until stiff and then folded into the cake batter before baking. Its aeration properties rely on both the quality of the meringue and the chemical leaveners.

A chiffon cake combines methods used with sponge cakes and conventional cakes. It includes baking powder and vegetable oil, but the eggs are separated and the whites are beaten before being folded into the batter, creating the rich flavor like an oil cake, but with a lighter texture that is more like a sponge cake. There is a lovely recipe for a chiffon cake here.