INGREDIENTS 1 pint heavy cream (aka whipping cream)
Pour the cream into a quart-size jar & add your starter. Whisk briefly to combine and cover with a muslin cloth. Culture at room temperature for 12-36 hours. The cream is done culturing when it's a little tangy, has thickened slightly and smells sweet and tangy.
Once cultured, place cream in the refrigerator for about 1 hour to chill. Next, use a stand mixer (with a splash guard), blender or butter churner to churn your cream. The cream will whip into peaks (1-2 minutes), then become grainy (2-3 minutes). Keep whipping until the solid butter mass and liquid buttermilk are separated (4-5 minutes total).
Gently pour the butter and buttermilk through a muslin cloth-lined strainer over a bowl. Transfer the buttermilk to a jar and store in the refrigerator. Be sure to save 2 tbsp of buttermilk for culturing your next batch of cream.
Remove the butter from the strainer and place it in a bowl. Add 1/2 cup of ice water to the bowl. Using a rubber spatula or butter paddles, fold and press the butter into the ice water. It will quickly become cloudy as remaining buttermilk is drawn out into the water.