Chocolate Mousse gone wrong. Why?

[maybe09750sender]

Dd wanted to make a chocolate log from Delia.
Cake bit all fine.
It has a mousse layer which has gone wrong.
We melted chocolate over hot water. Beat in egg yolks. Allowed it to cool a bit then in went egg whites. But instead of being moussey, its gone all hard again as if the chocolate has reset

Any ideas?

Oh sorry excuse secretsanta name change name!

Daft question but did you beat the egg whites?

Yes, whites have to be stiff.

Yes, peaked egg whites!
Should I have used a very good dark chocolate? It melted beautifully, really smooth, just started going all solid again when we put in egg yolks and even worse after whites.
PS I can't be bothered to name-change back again, just don't out me on the secret santa thread!!

How long did you leave it before folding in the egg whites? You did fold didn't you? If you beat them in then that could be why - you may have beaten all the air out.

Did you over heat the chocolate as it can "seize" if you do.

i could have done either of those things.
Ah well better luck next time. Dd not too worried, just curious. Thanks for your help.