Well darn it. This really bothers me, and Im sorry.
It might be the vinegar. Half and half should be no problem, just longer to thicken.
Ive made this many times.
I reduce the acid with the shallots to almost dry. I add in the cream, and start reducing.
I do know if the acid reduction is left too thin, it can curdle, it needs to be au sec, almost dry.
Theres so little liquid left it should not curdle or separate.
The wine reduction can be done over medium high heat-- after the cream is added, no more
than a medium heat--too high a heat can separate cream sauces.
It browns a bit while the cream reduces, giving it the tan gold color.
What exact acids etc did you use?
I need to get some ingreds togther before i can make it again. And I'll use half n half.
I feel awful yours didnt turn out, LNG. We'll solve it.
If you do try it again sometime, use Cream Sherry only and no vinegar.
Did you make the chicken, or just try the sauce?
I will have a go at making the sauce to see how it works for me. I just need to get some cream - although I do have vegan cream so could use that. But then I wouldn't be replicating the recipe...