Place sticks of butter in saucepan over lowest heat possible allow to melt without stirring. Once butter has melted the milk solids will float to the top and separate away from the butter fat. Carefully skim off with spoon, trying your best not to scoop any of the butter fat up. Pour through a tight mesh strainer or cheese cloth in to a glass container. Allow to cool, cover with lid, and store in refrigerator for up to 6 months.