I was excited reading Bittman's recipe in the NY Times food section last week for Browned and Braised Chicken with Root Vegetables. It sounded homey and just right for a Sunday dinner.

So what happened? I used half and half (which recipe said is ok) and the whole thing curdled, there was a ton of scum/foam at the top, and a big layer of grease as well. I understand the scum and grease (skin was still on the chicken, so that probably had a big hand in it), but what makes the cream curdle and how do I avoid it? If any of you DR cooking experts have feedback, I'd appreciate it!

What was the temperature of the cream when you poured it in?
Cold cream poured quickly into hot fat = curdling. The scum on top was probably the fat from the cream not the chix skin.

To help keep cream from curdling, either a)temper it or b)heat it in a small pan on the stove before adding to big pot.

What Joe said... but I'll also bet a big part of the problem was using half-and-half, which can be very prone to curdling, especially if you brought the mixture to a boil (which the recipe suggests). Cream is much more stable.

Ahh...thanks for the input. Yes, I added the half and half cold, so that probably did it. Next time I'll try warming cream up beforehand (and I'll try something more interesting than the carrot/celery/potato mix for vegetables).

I wouldn't use half and half at all, if it is going to be cooked for a while and not just added at the last minute. It doesn't have enough butterfat -- I'd use heavy cream or creme fraiche. Milk or half and half can curdle, unless there is some starch to stabilize it. Also, if there is any acidic ingredient like wine or lemon juice in the liquid, it will curdle half and half but not cream.