Listening to the Milk Street podcast, I learned something useful about dairy sauces.
According to the hosts, there are only two types of dairy that won’t break or curdle when boiled. Those are creme fraiche and heavy cream. Everything else needs to have some sort of starch to keep it from curdling if it boils.
I tried this recently when making some scalloped potatoes. I made a roux with equal volumes of butter and flour and then added the milk and cheddar cheese soup and brought that to a boil before pouring it over the sliced potatoes and baking them. Usually the way my mom has made scalloped potatoes, she’s just used milk and cheddar cheese soup and by the time the dish was done baking in the oven the milk would have curdled a bit. This time with the roux that didn’t happen.
Most of the time “starch” would be something like flour in a roux, or cornstarch or arrowroot powder in a slurry. In one of the previous episodes I’m pretty sure there was speculation abut using chickpea flour as a stabilizing starch in yogurt curry sauces. I’ve yet to try that.