How to make Cultured Butter

To make whey strain yoghurt or milk kefir through some muslin/cheesecloth/coffee 
filter.  I use a coffee filter in a plastic funnel placed over a jar to collect the whey.

Add some whey from yoghurt or milk kefir to cream and leave to ferment at room 
temperature covered with a cloth.   ½ cup whey per 500mls cream would be about 
right. When taste is to your liking blend in food processor with a little salt.  After some 
minutes it will separate into butter and buttermilk.  Pour the buttermilk into another 
container using a spoon to press buttermilk out. That's it although you can do an extra 
step by pouring ice cold water into blender and blending for another 30 secs. Pour off 
the water.

If you want to make butter a little softer you can add some olive oil towards the end of 
the process.

There are many uses for the buttermilk which is a by-product of this process so make 
sure you don’t throw it out.