Peel the cucumbers and chop them. Put the cucumber peel in 1 pint of good stock, bring to the boil and simmer for ¾ of an hour. Strain, and return to the saucepan and thicken with a little flour browned in butter. Bring to the boil, add 3 or 4 tablespoons of mushroom stock, and stir. Just before serving add the chopped salt cucumbers.