Submitted by Chaya Sara Fisher   Our family is made up of many gifted home cooks and our combined recipe repertoire is enormous. But when the occasion is serious, like an impending engagement, the question everyone asks is “Who will make the sponge cake?”   Sponge cake, an old family recipe, initially made by my grandmother’s mother, is my signature cake. Elegant in its simplicity, yet simple enough for Shabbos at home, it is our house specialty. My grandmother taught me to make it as a teenage; it was her specialty before she developed Parkinson’s. Now I make it for her and for my family, just the way she taught me.   The ingredients are basic, this cake is all about technique.