Combining melted chocolate with eggs I've come across a number of recipes (the most recent of which was this) which suggest various combinations of adding hot melted chocolate to a mixture that contains eggs.

The problem that I have here is that if I let the chocolate mixture go cold, it hardens and can't be mixed, and if I don't, it cooks the eggs.  I've tried stirring the mixture as the chocolate is added, which seems to be the most common suggestion, but it makes no difference.  Can anyone offer any other methods of avoiding scrambled egg cake?
The cocoa butter in your chocolate melts fully at 43 degrees Celsius (110 F). But it stays liquid until at least 30 degrees C (85 F). 
The most heat sensitive proteins in an egg white coagulate at around 65 degrees C (145 F), most proteins stay stable until 85 degrees C (185 F). 


As you shouldn't overheat your chocolate anyway, you have a certain temperature range where the chocolate will stay liquid, yet the egg unaffected. 

Note that the real problem and culinary art therefore is not the coagulating egg, but the effect of warm chocolate on any "foam" you might have produced in an earlier step: Too warm, and the bubbles might pop, too cool and the chocolate will harden as the cool other ingredients take up too much heat before it is fully incorporated.

Rule of thumb:
Melt the chocolate gently and let cool until barely warm to the touch. Stir quickly, yet gently, when incorporating the liquid chocolate into your batter.
(And read the recipe in case you need to deviate from this.)