Four large cucumbers, one small onion, half a box of gelatine soaked in half a cup of cold water, salt and white pepper to taste. Peel the cucumbers, cut into thick slices and place, with the sliced onion, over the fire with a scant quart of water. Simmer for an hour, stir in the gelatine and, when this is dissolved, season the jelly, strain it and set aside to cool.