Cream still has some whey in it, and whipping it just suspends it, where fully churning or overwhipping it separates it out so the remainder is purer fat
One interesting thing you can do in order to separate the whey from the fat in cream is (something very much like) freeze-distillation.
There is a cold spot in my refrigerator (not the freezer!) where the ambient temperature is approximately 25 °F. If I put a carton of heavy cream there, in several days the contents will have largely separated—there will be a solid chunk of milkfat, and some liquid whey.
Having drained the whey, I can then beat the milkfat with an electric mixer. This causes the remainder of the whey to separate out (due to centrifugal force); after draining this remnant whey, I am left with butter.
One interesting thing you can do in order to separate the whey from the fat in cream is (something very much like) freeze-distillation.
There is a cold spot in my refrigerator (not the freezer!) where the ambient temperature is approximately 25 °F. If I put a carton of heavy cream there, in several days the contents will have largely separated—there will be a solid chunk of milkfat, and some liquid whey.
Having drained the whey, I can then beat the milkfat with an electric mixer. This causes the remainder of the whey to separate out (due to centrifugal force); after draining this remnant whey, I am left with butter.
If part of my fridge were below freezing I would find that very frustrating, but it sounds like you’ve figured out how to use it to good effect!