Has any one tried doing this with a canner? (Big pot, comes with a rack to hold& raise a bunch of canning jars off the bottom. Fill pot with water to recomended level). Preforms same service as double boiler, takes less space, ease of use at sm expence. Never made butter my self, just came from long line of good southern cooks & seems to me mightbe a work/space saver. They usually come with tongs shaped to grasp & hold canning jars.
PEACE