Add dry ingredients to mug and mix well. Add the egg and mix thoroughly. Pour in the milk and oil and mix well. Add the chocolate chips, if using, and vanilla and mix again. Put your mug in the microwave and cook for three minutes at 1000 watts. The cake will rise over the top of the mug, but don’t be alarmed! Allow to cool a little and tip out onto a plate if desired. EAT! This cake can serve two if you want to feel slightly more virtuous. And why is this the most dangerous cake in the world? Because now we are all only five minutes away from chocolate cake at any time.