Pour heavy cream or whipping cream into a mixing bowl of your stand mixer, and attach the wire whisk/whipping attachment.
Turn on the mixer and start whipping the cream at low speed. Gradually increase the speed to medium and then medium-high.
Initially, the cream will start to thicken, and then it will turn into a soft-peak whipped cream.
Then it will turn into a cream with stiff peaks. Continue mixing; the cream will start to become grainy.
Continue whipping, and soon you will notice butterfat separating from the buttermilk. At this point, cover the mixer with a kitchen towel to prevent splashing of buttermilk all around.
Keep mixing until the butterfat is wholly separated from the buttermilk. Also, the butter will solidify and stick to the whisk attachment.
Once the butter is solidified, pour off the buttermilk into a mason jar for later use. Then using a rubber spatula, remove the butter from the whisk attachment and place it back into the bowl.
Now we need to rinse the butter to remove all the buttermilk to enhance the shelf-life of butter.
Pour a cup of ice-cold water over the butter into the bowl, and rinse the remaining buttermilk by running mixer on low-medium speed. Make sure to cover your mixer with a kitchen towel to avoid splashing.
Again, drain the water collected at the bottom of the mixing bowl. Do not keep this water, as there is no more usable buttermilk at this point.
Continue rinsing the butter with ½ cup of cold water until water runs almost clear. It could take 2-4 times of rinsing. Keep draining any remaining water.
Using your spatula, remove the butter from the whisk and put it back into the bowl.
Keep pressing the butter with the spatula onto the side of the mixing bowl to remove any excess buttermilk.
Transfer the butter into a muslin or cheesecloth, and press tightly to ensure maximum water removal from the butter.
Remove the butter from the cheesecloth, and place it in an airtight container. Or at this point, you can add salt, mix well and then store.