The essence of most cakes is sweetness and richness. A cake is a web of flour, eggs, sugar, and butter (or shortening), a delicate structure that readily disintegrates in the mouth and fills it with easeful flavor. Cakes often contain more sugar and fat than they do flour! And they serve as a base for even sweeter and richer custards, creams, icings, jams, syrups, chocolate, and liqueurs. As suits their luxurious nature, they’re often elaborately shaped and decorated.
A cake’s structure is created mainly by flour starch and by egg proteins. The tender, melt-in-the-mouth texture comes from gas bubbles, which subdivide the batter into fragile sheets, and from the sugar and fat, which interfere with gluten formation and egg protein coagulation, and interrupt the network of gelated starch. The sugar and fat can compromise lightness if they weaken the cake structure so much that it can’t support its own weight. Of course dense, heavy cakes can be delicious in their own way. Flourless chocolate cakes, nut cakes, and fruit cakes are examples.