Pour heavy cream into a large bowl and add in the yogurt, stir to combine
Cover with a dish towel and let it sit at room temperature for about 48 hours until thickened
Pour the mixture into a stand mixer and whisk on medium until you have butter, first you'll have whipped cream, then the butter will separate from the buttermilk
Strain the buttermilk into a bowl and put the butter into a bowl of ice water
Squeeze out excess buttermilk from the butter
Empty the bowl and do another round of ice water and squeeze again until water is clear
Add sea salt to taste and mix well
Form into a ball, wrap in parchment paper or place in an airtight container
Store in the fridge for up to a month
