Some people use xanthan gum for thickening. About 1/4 - 1/2 tsp. per cup of liquid shopuld do it.

I like the "natural" approach. I either reduce the cooking liquid - it helps if you start out with a stock as the braising liquid for its thickening power - and then add a bit of cream and reduce it even further. Or, I use cooked and well pureed cauliflower.

Karen