No need for the Roll Eyes.

First, the text you quoted states that this will happen only with one or two drops of water. Not with a larger quantity. That's what I said. It also states that it is odd it will do it with 1-2 drops but not with more. However, it fails to provide an explanation.

Second, Cloudship did not add water but batter. Batter is not water.

Third, it stands to reason that the batter was not added in quantities of 1-2 drops. So it shouldn't have hardened if the reason was water.

Sadly, we still don't know the real reason. I have never had chocolate harden whether I used a bain marie or not.

We can presume a temperature reaction, Cloudship said she let it cool 20 minutes, in that the temperature of the mix dropped to quickly when a colder substance was added. Or we can presume a chemical reaction, as would be the case with water but since water is not batter, see above.

The reason that the text doesn't recommend butter is that butter still contains water. Oil doesn't, as he says.

Cloudship, how did the cake turn out? And what was in the batter you tried to mix with the chocolate?

Till