Ski, I’m so pleased you posted this question as I had the same thing happen to me last night. I have made many batches of mousseline and they have all been pretty soft. However, when the sugar was on the heat the doorbell rang and when I got back to the stove I popped the thermometer in to the syrup and pulled it off when I saw it hit 248. It MAY have been a bit higher than this but I didn’t hang about to see! I then whipped the meringue longer than I normally do before starting to add the butter - it seemed stiffer. Adding the butter was pretty normal except that the ‘curdling’ took a while to disappear. From then on I noticed the mousseline was stiffer than normal. BTW I just ignore the curdling phase and battle on regardless - it always comes together in the end.
I found the mousseline easier to work with and pipe and would actually quite like to reproduce the stiffness each time I make it. Does anyone have a tried and tested method of controlling the stiffness of mousseline?
Another question I have is: what is the ideal temperature of melted chocolate for chocolate mousseline? I melt chocolate and let it cool - but not to setting point - while beating in the butter. The last time I made it the chocolate hardened as it was being poured in to the bowl and I got lots of small chocolate lumps in the buttercream. Should chocolate be re-tempered and is there an ideal temperature so that it blends rather than sets?
One more thing I discovered for passion fruit mousseline - one of my favourites. I didn’t have time to make PF curd so just reduced the juice to 50% (by weight) and used it instead. Wow! An intense PF experience - I think I’ll skip the curd from now on unless I need it for something else.
I was going to start an new thread for all this but see Ski already started with the same question.