Which taste better, does butter still leave the cake moist like oil? I was thinking about doing a combination of both butter and oil for cupcakes.
in my tests--butter did not perform as well as oil
i chill all my cakes
the butter cakes in my tests did not come back to room temp as well as oil based doctored mix cake or recipe (scratch) cake
the butter cakes in my tests--still stayed firm in the mouthfeel and when it was swallowed had that 'dry' full feeling down the throat--scraped a little going down
if that same butter cake was microwaved very briefly--it was perfect as any other cake--so it was not dry at all
but the butter held up too well --did not loosen up like oil does--when coming back to room temp and created a problem in my test cakes that i can easily avoid by simply using oil--most of my fillings need chilling so that was that
so i used oil based for all but family cakes
those are my observations
i don't know that there's just one key thing to it
but buttermilk is a very important ingredient for added goodness, can easily be subbed for other liquids.