Put cream into a jar and add yogurt. Stir well and close the lid.
Leave on the counter for 24-48 hours until cream is completely firm.
In a bowl or stand mixer, whisk until the buttermilk separates from the fat.
Drain the buttermilk.
Wash your butter until the water is clean.
Plunge your butter in a fresh bowl with ice and ensure it is no longer retaining buttermilk.
Add salt or anything else if desired.
Wrap up in baking/parchment paper and store in the fridge or freeze.
