Add the heavy whipping cream to your mixer, and mix on high speed. After 3-5 minutes, you should notice that the mixture will start have a "curd" like texture. This is where the butter fat is starting to seperate from the buttermilk liquid.
Drain the buttermilk liquid into a container, and save if you wantto use it for other recipes, like Buttermilk Honey Bread.
Keep the butter fat in the mixer, and add ice water, making sure no ice cubes get added. Mix the butter fat and ice water for about a minute.
Drain the water, and move the butter fat to a papertowl, and blot the butter well, making sure to get all the eftover liquid out of the butter. Add salt, or other herbs and spices!
Store the butter in an airtight container. It will stay good in the fridge for about 3 weeks!