Which french writer wrote about sponge cake?

It's not a specific writer who is known for writing about sponge cake. However, there are many French writers who have mentioned or incorporated sponge cake into their works in various ways. Some examples include:

* Marcel Proust: His famous novel *Remembrance of Things Past* features madeleine cookies, which are closely related to sponge cake.

* Honoré de Balzac: In his novel *Cousin Bette*, he describes a character making a "gâteau à la crème," which translates to "cream cake," and may have involved a sponge cake base.

* Guy de Maupassant: In his short story "The Necklace," he mentions a "gâteau de Savoie," a type of sponge cake.

Ultimately, it's difficult to pinpoint one specific French writer who wrote *about* sponge cake, as it's a common dessert that has been enjoyed for centuries and likely found its way into many literary works.