food film or a cotton towel to help contain the splattering) whip it until the curds of butter separate from the whey (buttermilk). this can take anywhere from 5 to 1o minutes.
once the buttermilk has separated from the curds pour the contents of the mixing bowl through a fine mesh sieve saving the buttermilk for cooking or to enjoy as a beverage.
place the butter curds back in the mixing bowl and pour ice cold water over it. using a small spatula or wooden spoon press out any remaining buttermilk. keep pressing and rinsing the butter until the water runs clear.
mix the sea salt into the butter according to your taste. 