I've actually had the same thing happen awhile ago but I chose NOT to substitute and the cake tasted just as good and family members didn't even notice a difference. I guess it became a low- fat chocolate cake. Which is a bit healthier! Great tip JodieF!! Thanks!
I can do all things through Christ who strenghtens me. Phillipians 4:13
Ok friends, my advice is DON'T DO IT!! I don't know if it is just cause I live at a high altitude (6500 ft), but even with the "adjustments" I always make this caused my cake to rise super high super fast, and then it collapsed in to almost nothing!! It is a sad, sad lookin' cake right now. I will wait next time until I have granulated sugar! This is a recipe I usually use, which usually turns out great with regular sugar, so I know that the powdered sugar was the culprit!!!