8 ounces heavy cream
Using a 16 ounce jar with a tight lid, pour in cream and allow to sit at room temperature for 6-8 hours.
Shake cream in the jar until a clump forms. This is the butter that has separated from the buttermilk.
Pour off buttermilk (save this for use in pancakes or waffles). Rinse off butter several times under cold water.
Add a pinch or two of salt to the butter and mix well.