Cut the stalks of the chard into pieces approx. 5 cm long and the leaves into ½ cm wide strips. Cook the stalks in the vegetable stock until soft, briefly blanch the leaves.
Chop the cucumber, lightly salt it and squeeze out carefully.
Mix the chard, tomatoes, olives, feta and rocket together. Season to taste with olive oil, balsamic vinegar, salt and pepper. Let it steep for about ½ - 1 hour. Mix the cucumber into the salad just before serving.