This is Creme Fraiche the very easy way:
Start with a pint of the best quality cream you can find (NO ultra-pasteurized cream). If you have it raw, all the better, but it is spring and the cream content of our milk is going down as the cows are now on pasture, so I cannot part with the cream from my milk.
Then, you are free to add 1 tbsp of either good quality commercial creme fraiche (as seen above), creme fraiche from a previous batch (so save some from this batch you are making), good quality commercial buttermilk, or your own homecultured buttermilk.
Mix it well, and cover it tightly.
Place it somewhere consistently warm for 20-24 hours, then chill (I have mine covered and labeled with a small paper bag on top of my refrigerator to help trap the heat as our kitchen is drafty).
The finished thick creme.
See, truly thick (I let mine go a few hours over 24 as well, so it's a bit extra thick).