Quark is a fermented milk product. It can have the consistency of cream cheese. I usually make it a bit more spreadable than cream cheese.
It can often be bought in health food stores, but I make it at home. Here's my instructions for making it: ISO additions to cream cheese or quark
Of course, all tools and containers should be extra clean and it's a good idea to scald them. If you scald the milk, make sure it cools off to max 60C (108F), but preferably slightly less, so it won't kill the micro-organisms.
I just tried using a slightly different method. I didn't heat the quark after it had clabbered. I just drained it a lot longer. Seemed to make a bit more and smoother texture. Be sure to save the whey. It's better to let the quark drain to a little too dry. You can stir in, a little bit at a time, some of that whey to make it the right consistency. A little bit of salt really perks up the flavour of the quark.
I have been told that the whey is good in pancakes and bread.