They actually passed the question on to their physics buff Alom and here is what he had to say about my the Life Chocolatic incident:
This is something that I have tried to do on purpose, believe it or not. The phenomenom is known as “superheating” and it’s quite spectacular to witness. Basically, due to the way a microwave oven heats things up, the liquid is warmed up beyond it’s boiling point, without the bubbling that we aassociate with boiling. Bubbles do not form in the superheated liquid, so high temperature vapour / gas is not carried away as it normally would be. This is an unstable state. As soon as you put an object into such a liquid (like a teaspoon), you make bubbles – lots of them very quickly, they explode out of the liquid and take lots of liquid with them. The same thing can happen if you put sugar in or sometimes even if you just knock the container.
Now this is an answer that even I understand. It certainly is quite spectacular to watch, and it is also quite spectacular how much you have to clean up afterwards. But it is interesting ! Cooking without bubbling, and I didn’t even do it on purpose.