To two pounds of fat (finely chopped if unrendered) add one-half pint of milk, preferably sour. Heat the mixture in a double boiler until thoroughly melted. Stir well and strain through a thick cloth or two thicknesses of cheese cloth wrung out in hot water. When cold the fat forms a hard, clean layer and any material adhering to the under side of the fat, may be scraped off. Sour milk being coagulated is preferable to sweet milk since the curd remains on the cloth through which the rendered mixture is strained and is thus more easily separated from the rendered fat which has acquired some of the milk flavor and butter fat.