Pour the cold cream, straight from the refrigerator, into the blender and secure the lid.
Start blending at medium speed, then gradually increase to high speed. After a few minutes, you’ll notice the cream thickening and turning into whipped cream. Keep going! I usually have to begin scraping the sides of the container and pulsing the blender at this point, as air pockets form around the blades. The cream will begin to separate into butter and buttermilk and you will hear a sloshing sound in the blender.
Once the buttermilk separates (you’ll see chunks of yellow globs floating in liquid buttermilk), stop the blender. Pulse it 3 more times for just a second or two each.
Once the buttermilk separates (you’ll see chunks of yellow globs floating in liquid buttermilk), stop the blender. Pulse it 3 more times for just a second or two each.
Transfer it into a bowl and pour cold water over it until the water draining runs clear. Use a spatula or your hands to knead the butter, rinsing out any remaining buttermilk. Change the water a couple of times until it runs clear.
If you like salted, sprinkle in a little salt and knead it in. Knead to press out any buttermilk before stamping, molding or storing.