Clean and wash the tomatoes, spring onions and mushrooms. Cut the tomatoes into slices. Cut spring onions into rings. Cut mushrooms into quarters. Wash parsley, dab dry and remove the leaves.
Mix the prepared salad ingredients and arrange on plates. Mix vinegar, salt, pepper and sugar and add oil. Pour the marinade over the salad and let it stand for a while. Cut Parmesan cheese into thin slices with a peeler and sprinkle over the salad.