Open up the entire top of the 200 ml carton of heavy cream, pour 50 ml of plain yoghurt, and mix well.
Let sit for 24 hours at room temperature with the carton top opened. When the surface hardens, it's ready to use.
Close the lid and store in the refrigerator.
Story Behind this Recipe
Using the recipe I got from a book, I adjusted it to an easy-to-make proportion.
Using the carton of heavy cream makes preparation and storage easy. The higher the temperature, the faster the fermentation. Give it a shake test; if the surface doesn't move, it's time to store it in the fridge!