I found with GV butter, there is a lot of "milk" left over after pouring off the fatty good stuff. Also if I left any of that in the jar during canning, my butter had litthe brown specks. Fine for cookingb though.
I canned my ghee for a full 75 minutes. I think if I was doing whole butter, I'd do 30.
Sad but funny story. I read in one of Miles Stair's books instructions on just melting the butter, pouring it into jars, and putting a simmered lid and ring on it. Apparently his wife Betty did it that way. Well, so did I. 20 pounds of butter that way. Lost every single jar. Literally molded in sealed jars. Yes, I sterilized the jars. After that I have always pressure canned my butter.