Place cream into Thermomix bowl and warm 8 min/37°C/speed 2.
Add yoghurt or creme fraiche and stir through 15 sec/speed 2.
Pour into warmed, sterilised glass jar or Thermos flask and keep at temperature for 12 hours. The glass jar must go into a yoghurt maker or similar to stay warm…this can be up to 24 hours or even longer, within reason…a week is too long.
Chill the newly cultured cream until totally cold…colder the better.
Return cream to a COLD Thermomix bowl with Butterfly attached. Whip until separation occurs. This took a long time for me, and I think it is something to do with the heating of the cream previously. Drain off the buttermilk after you have separation and voila, you have Cultured Buttermilk as well…(cultured butter, ergo; cultured buttermilk from the butter!!)
Place the butter into a simmering basket and insert into the Thermomix bowl.
Pour over iced water to just cover the base of the simmering basket. Rinse or wash the butter by running the blades for a few seconds on speed 8-9 and hit reverse a couple of times. Drain off the water and press out the butter squeezing out as much liquid as possible.
Press into a butter bell or roll into a piece of parchment paper and use in great lashings! (add salt if you wish.)