Well, the mug that I was using was a bit smaller than the one I used in Montreal, so I decided to use slightly less of each ingredient (well ok, except for the cocoa. and the sugar), and we don't have measuring utensils or a clean teaspoon, so I had to eyeball it. Anyways, my roommate and I had a brief moment of excitement when the vinegar went in on top of the baking powder and fizzed, then I mixed it all up and we were back down to business. I popped it in the microwave for a safe 2 and a half minutes (I'm not sure how British microwaves compare to Canadian ones, so I didn't want to overdo it) and sat back to watch the show.
All of a sudden it started growing. "Not to worry," thought I, "this is to be expected." But then I noticed that the part that was growing (rapidly) above the rim of the cup looked significantly more liquid than it should. As I watched, it started spilling over the side of the cup, and with the speed and agility of a panther on meth I popped open the microwave, grabbed the mug and rushed over to the dishes drawer (yes, drawer) where I carefully held it over a plate until it stopped spilling over. My roommate Naomi was there to catch the single wayward drip. So, as the batter was still, well, batter, I put the mug on the plate and put it back in the microwave.
Naomi and I spent the remaining two minutes and seven seconds watching the contents of the mug bubble and froth, spilling over the edges of the mug and on to the plate. When the microwave dinged and we opened the door, this is what greeted us:
Well, the moral of the story is this: if you're going to attempt to make this at home without eggs, go easy on the baking powder and vinegar (I used white, btw). In addition to the aesthetic problems associated with this particular experiment, there was a distinct taste of, well, baking powder and vinegar. There are probably a variety of factors that contributed to this: the lack of appropriate measuring utensils, my perhaps too enthusiastic use of this particular egg substitute recipe, the lack of vanilla... I could go on. The cake was definitely edible, but not as delicious as I have had it, which was disappointing.
Anyways, good luck in your egg-substituting endeavors. And learn from my mistakes!