Pour heavy cream in a stand mixer bowl and whisk on low speed. You can also use a blender, food processor, handheld mixer, or shake in a mason jar.
2 cups heavy cream
Increase mixer speed when cream begins to thicken. Continue whisking until whipped cream curdles, then you'll see the butter separating from the liquid. Reduce speed. Depending on your mixer and speed, the time this will take will vary.
Transfer all the butter into a bowl of icy cold water. Sieve the remaining buttermilk and store in fridge in airtight container.
Rinse butter thoroughly and squeeze until all excess buttermilk. Sprinkle on salt, if desired. Store in wrapped parchment paper, cling wrap, or airtight jars.