I have been cooking my butter for 8 to 10 hours and the results have been very satisfactory. I use 2 oz of good trim for each lb of butter. The butter has been very successful but the cream has been awful. It was so bad it made the ice cream almost inedible. It is totally chronic though. Adding more sugar and berries could still not kill the taste. Anyway the butter is easy. Just melt the butter and add the trim bring to a simmer then cover turn down to the lowest setting for 8 to 10 hours. Strain with cheese cloth.