Re: Cobasan, it has been a while since I read about it, but I think it only works with non ultra-pasteurized cream which I have found impossible to buy.

Matthew, I’ve found non ultra-pasteurized cream for sale at a local fruit farm that sells some specialized dairy items.  It’s twice the price of ultra-past. found in the grocery store, but it’s absolute heaven!

PS - thanks for the yogurt tips.