Soreen and a block of marzipan. Cave-proof and calorie-dense. Also feels like eating Christmas Cake if you have them together. Now all you need is a block of mature cheddar to go with it.
A Peveril Stores cherry and chocolate flapjack usually does me, but the Soreen mention reminded me of their recipe for a malt loaf flapjack - that surely must be the pinnacle of cave food? In fact I may have to try this:
Rice crispie cake is another easy one to make that's robust enough for taking underground - melt some butter in a pan, chop up some mars bars and melt those in the butter, stir in a load of rice crispies, pour into a tray and leave to cool.