AI made a cute simple sesame street cake at night and in the morning the buttercream was saggy and had some cracks. Do you think I was short on the powdered sugar?
How long after you filled and stacked the layers did you frost it? Cake settles, so I like to let it sit for at least a few hours before frosting or covering with fondant.
I'm not sure how the butter/shortening ratio comes into play in this since I've always done mine the same way but definitely give your cake time to settle before frosting it.