Remove the skin from the pumpkin and cut into pieces,making sure that the pieces are not too thick.Place the pumpkin into a large pan,pour 1kilo of sugar over the pumpkin and leave for 2-3 hours.Then cook the pumpkin and sugar over a low heat without adding any water as the pumpkin will give out water as it cooks.Do not cover the pan tightly or the water will boil over.Cook until softened and serve cool sprinkled with walnuts.