Place cream in a blender. Add salt if desired (1 tsp per cup of cream or more to taste).
2 cups Cream, 2 tsp Salt
Blend for a few minutes on and off (or you can shake it in a jar until it starts to ball together and separate from the buttermilk). Use a spatula to push butter together into a clump.
Pour off buttermilk. Save for another recipe like buttermilk biscuits.
Pour iced water over butter (just enough to cover) and blend for another 30 seconds to wash the butter (remove any butter milk). This will make it last a lot longer in your fridge!
Pour off iced water and place butter in a dish. Refrigerate and use.