Has anyone got any advice for making the sponge in cupcakes more dense/moist? I made some chocolate ones last week just using a 2 eggs/4oz everything else mixture with some extra milk and melted chocolate, with thick buttercream piped onto the top in a swirly pattern. They were quite nice but only lasted a couple of days before the sponge bit was rock hard. They looked very pretty and I want to make some for my friend who's just had a baby but I'd like them to last a bit more than 2 days - the buttercream is lovely but so sweet I couldn't manage more than one cake in a day.
I've heard that either swapping the butter for oil or adding buttermilk might help - but haven't used either of those before so not sure which to try. Anyone got any tips? Would be v grateful for any advice.