Strip the currants from their stalks, then weigh them and put into a preserving pan with the sugar and the water. Allow the pan to stand at the side of the fire until the sugar begins to dissolve, stirring occasionally. Now place the pan on the fire, again stir until all the sugar dissolves, and then allow the ingredients to boil for one-half hour.
The butter should be added when the jam comes to boiling point.
Test a little of the jam on a saucer, and, if it stiffens at once, pour into jars, cover when cold.
The butter prevents the currants from becoming hard.