Clean and halve the mushrooms. Leek onions clean, wash, dab dry and cut into rhombs. Tomatoes wash, dab dry and halve. Mix vinegar, mustard, salt and sugar, fold in olive oil.
Wash the thyme, put something aside for garnishing. Pluck the leaves from the stems and chop them finely. Stir into the vinaigrette. Heat the oil in a frying pan. Sauté the mushrooms for about 5 minutes.
Add spring onions and tomatoes and fry briefly. Mix the mushrooms, spring onions and tomatoes with the vinaigrette. Cut curls of parmesan cheese with a peeler. Garnish salad with parmesan and thyme.