Combine the yogurt and cream together in a large container like a cambro or a bowl with plastic wrap.
Place the cream on the counter for 48-72 hours or until the cream looks thickened and smells slightly tangy.
Put the thickened cream into a stand mixer with a whisk attachment and whisk on medium speed until the fat separates from the buttermilk.
Prepare three large bowls of ice water and set them aside.
Place the soft butter curds into the first bowl of ice water until they firm up.
Squeeze the butter curds to remove as much buttermilk as possible.
Move the butter to the second bowl and continue washing the curds.
In the final bowl of ice water the water should be clear after washing.
Place the cold butter onto a wooden cutting board and pound it flat with butter paddles or a wooden spoon.
Wipe up any water with a paper towel or towel. Try to remove as much water as possible while continuously compressing the butter.
Add in your salt or preferred seasonings and mix it into the butter.
Shape the butter into a rectangle with your butter paddles and then enjoy or freeze for later.