I thought back to my roots. Filipinos have this sort of cake/cookie called a Mamon Tostado which is essentially toasted pieces of Sponge Cake. It's a Filipino Biscotti, if you will. It's crunchy and slightly sweet. Perfect for dipping into coffee. So if you made a sponge cake and find out that you have run out of ingredients for a frosting, make Mamon Tostado.