Wash the strawberries and drain well. Place in a large bowl in layers with the sugar, cover and leave for 24 hours.Then place the contents of the bowl in a greased preserving pan or a large thick-based saucepan; heat slowly, stirring, to dissolve the sugar, then bring to the boil and boil rapidly for 5 minutes.
Return the mixture to the bowl, cover and leave for a further 48 hours. Add the sugar and stir over a gentle heat until it is dissolved.
Then return it to the pan, bring to the boil and boil rapidly to setting point, about 10 minutes.
Allow to cool until a skin forms on the surface; stir, then pot and cover in the usual way; label and date. (See 'Potting and covering' for details).