i think either of you could answer my question abotu my first fallen butter cake this evening!!!

i have baking a coffee & chocolate butter cream cake for ages but it failed for the first time on my today!!! the only different stuff i added in the recipe was the 1 t. ovalette... i thought since it could make cakes more spongy, i decided to add it in my cake... boy, when the cake was being baked, i could see the cake doubled the "height" from the glass door. you woulnd' know how happy i was going to have a spongy butter cream cake... was i wrong... the cake sank once it cools down. it couldn't even been cut as it was so crumbly and couldn't hold it's shape... :( maybe ovalette is only used in the sponge cake recipe??? pls. help!!!

ps: i am going stick to my normal butter cake from now on!!!