I have tried to make a chocolate cake recipe where you add the coffee to the end of the mix. Then I read in Baking Illlustrated and in The Cake Bible where you get a deeper chocolate flavor if you dissolved the cocoa before adding it to your batter instead of mixing it in with the flour.

So I took the chocolate and dissolved it into the coffee, and then added that to the sour cream and extract (as per BI book) and added it to the batter that way. The cupcakes were definitely drier than the first batch after cooling.

So does anybody know why adding the coffee at the end makes for a moister cake? What is the science behind this?

Thanks.

I don't know that adding coffee to choc cakes makes them moister, I add dissolved instant coffee to my choc cake recipes to enhance the choc flavour. I've made choc cake with and without coffee and haven't notice a difference in moistness.