I have no experience with this particular sitaution, but I looked up the errata for TPPB, and didn’t see anything. But…I did come across this post by Julie which may be of some help to you. Perhaps she will chime in with advice.
This is a question by sue:
I am a trained pastry chef and a great admirer of your books. All your recipes have been exacting and fool proof until recently. I made the caramel ice cream out of the pie and pastry bible and had a great deal of trouble incorporating the hot milk into the cooked sugar. Much to my dismay, the mixure kept curdling. I strained it but there was lots of residue. I then made the anglaise and tempered it with the caramel that had been strained out. I still wasn’t happy,...the mixture didn’t have the caramel flavor I wanted and there was still a lot of curdled residue in the strainer. I then poured the entire mixture into the blender and voila, everything came together. I restrained the mixture and there was very little residue this time. Finally, I added the caramel custard mixture to the cold heavy cream that had vanilla bean seeds in it. The recipe was written so that the hot milk was added into the cooked sugar and reduced to 3/4 cup. The problem is that milk can’t stand up to this kind of cooking. Wouldn’t it have been better to add part of the heavy cream to the caramel instead and then add all that to the anglaise and finally the heavy cream (minus 1 cup cream/add 1 cup milk) steeped with vanilla bean seeds. Anyhow, that’s how I would make it on my next try.
Sue, I’m not Rose, but was able to solve a similar problem with curdling caramel creme anglaise. In my case, the problem turned out to be that the caramelized sugar was becoming too acidic, so that adding the hot milk to the acidic sugar resulted in curdling.
For me, the acidity was both from using blonde organic sugar (which has a bit of residual molasses), and from taking the caramel a bit too dark (the darker the caramelized sugar, the more acidic it becomes).
When I switched to refined white sugar and used a thermometer to make sure it didn’t exceed the recommeded temperature, the problem disappeared.
Hope that helps!
The rest of the discussion is here:
Hopefully this is of use to you.