I was making dessert in my summer warm kitchen and when whipping cream the cream turned nearly instantly to butter. Luckily it was still unsweetened and so I took the butter clumps out to wash them and use them as delicious homemade butter. The buttermilk was at this point not fermented, so I decided to inoculate it with some creme fraice from the fridge, thinking: if you can use buttermilk to inoculated cream for creme fraiche it will work the other way round, too. And it did! After 24 hours the buttermilk was thick and tasted sour.
But what should I do with this tiny amount? Making bread with buttermilk is always great and so I decided to put it into the dough I was kneading for the bread baking in the wood fired oven in the local museum.