Just a bit of information on canned butter. If you are interested in storage of canned butter then you can do a Google search for "canned butter". Almost all of the canned butter being sold in the U.S. comes from an Australian company called Ballantyne. They make six different brand names of butter (see pic below).
Be wary of recipes for canned butter that you find on the internet. There are a number of problems with this method. Please see this post for cautionary information.
http://www.uga.edu/nchfp/questions/FAQ_canning.html#33
