Buerre de Baratte from Rudolphe Le Meunier @ Cheeseboard, Berkeley
I just read about how wonderful and rare this fermented French butter is and, lo and behold, I walk into Cheeseboard it's sitting pretty in their takeout section. $7.50 for 250g.
Nice spotting! I read that piece a few days ago too. Boy, that blogger does not know how to spell. Not even the name of the product nor the producer.
This is it (if you care to edit your title):
Beurre de Baratte
Rodolphe Le Meunier
Here are some photos of a baratte, the old-fashioned hand churn used to make this type of butter.
ETA: Quite a few local shops carry the cheese from this affineur. I bet we can find it elsewhere too. Here's more about Rodolphe Le Meunier on the Cheese board. Please check it out if you're a cheeselover.