I made this chocolate cake the other week. I omitted the chocolate chips, used soya milk instead of water, and it worked beautifully. Tonight I tried it again, and the only difference was that I omitted the vanilla as well, and used coffee as the recipe suggested to make a mocha cake. I made the coffee by mixing up instant coffee with a bit of boiling water, then adding cold soya milk to bring it up to the required quantity. The cake didn't work. It was all gooey inside, and even with an extra 20 min in the oven, it's still got a varied and rather odd consistency. Every other variable was the same, so I'm wondering whether it's some sort of chemical reaction with the coffee. Does anyone know more about how this works?