Bread and Butter Pickle

Layer the cucumber and onion slices in a large bowl, sprinkling each layer with salt. Leave for 1 hour, then drain and rinse well. Put the vinegar, sugar and celery and mustard seeds in a saucepan and heat gently, stirring, until the sugar has dissolved. Bring to the boil and boil for 3 minutes. Pack the vegetable slices into preheated jars and add enough of the hot vinegar mixture to cover. Cover immediately with airtight, vinegar-proof tops. This pickle must be stored in a dark place or the cucumber will lose its colour. Store for 2 months to mature before eating.