Geoff Scrase of Lower Hutt writes:
Butter can be made from cream more cheaply than a present pack of 500g (about $6) if it is made from a 2-litre bottle of cream (about $8.50 plus GST from Moore Wilson). A 2-litre bottle should yield about 900g of butter and the balance of the mass is buttermilk. Beat the cream until it separates into butter and buttermilk, separate the two then pat the butter into shape. The buttermilk can be added to standard full cream milk, as it is not cultured, with little change to the taste of the milk.