use an old mayo jar with a good tight lid. place a few marbles in the jar.
pour cream to about half a jar. add your salt. i never add more than a tsp. you can always adjust the salt to your taste the next time you make this. YOU WILL MAKE THIS AGAIN!
put the lid on tight. i wrap a towel around mine because it tends to sweat and the jar gets a bit slippery. now...shake like crazy. this will require changing hands...alot of shaking going on. just keep on shaking. when you think it will never end..shake some more!
you will peek...and it will look like frosting or melting ice cream...shake more. then sooner or later...usually later...you will see that it has become watery and you will think it has messed up. but that means you have succeeded and you have made butter! pour off the water and put it proudly in your bowl!
gotta keep it refrigerated or it will spoil. it will get very firm in the refrigerator. but it is worth the chiseling. and if you know you are going to want it for a meal...just set it out while you are cooking and let it soften.
be prepared...this stuff is like gold...it will go fast!