The most important thing to note is that the heavy whipping cream has to be shaken or beaten by arm strength or by a stand mixer or hand mixer. The whipping cream will need to gradually increase to the highest speed (you'll want to cover the bowl for splashing or the jar) and get it to split.
You can stop for just a little bit of time and you have to continue to shake or mix until you start to notice the fat separate from the buttermilk.
You'll drain the buttermilk, unless you want to save it, and you can squish out any excess buttermilk from the fat. The less buttermilk the longer it lasts (up to 3-4 weeks).
Take the ice cold water and pour some over the butter. You'll continue to drain the bowl and pour the cold water over until it has turned clear.
From there you can store it or you can add the garlic, basil, parsley. Pink Himalayan salt is optional as well.
Place in the fridge after storing or start spreading it all over everything.