Wash and clean the cucumbers and slice them into very thin slices with a vegetable slicer (alternative: cut them into thin slices with a sharp knife). Put cucumber slices in a bowl. Sprinkle with 1 tablespoon of salt.
Leave to infuse for about 30 minutes.
In the meantime peel and finely dice the onion. Boil 300 ml water with onion, sugar, mustard seed, laurel and vinegar. Simmer for about 2 minutes.
Pour the cucumbers into a sieve, drain well and then pour into the glasses. Pour over with hot stock, close well and let cool down. Keep cold until you eat them.