I have an old, tried and true chocolate mousse recipe that I've had no problem with in the past. Found it again and decided to make a moussecake at the new place. The only difference is the chocolate. In the past I'd shave pieces off of a large slab, Guittard, Ghirardelli, etc. At the new place we carry an El Ray chocolate, and it comes in little discs. I don't know if that is making the difference, but it's the only variance. Anyhow, I melt the chocolate completely in a double boiler, then slowly incorporate the egg yolks, then add rum and coffee. I finish with the whites and cream (both whipped of course). This usually results in a light and creamy mousse, but after the cake has set I see that the chocolate has seized. I thought maybe it was because the coffee was cold so this week I made sure it was still hot. Even worse seizing this time. I'm stumped. Do you think it's the chocolate? Or am I missing something. Any help or guidance you can give me is greatly appreciated.