Clean the mushrooms and cut into slices. Halve the cucumber lengthways and cut into thin slices. Cut the bell pepper into thin strips and then cut in half. Put everything together.
Slice the parmesan into small pieces and add to the salad. Separate the thyme leaves from the stem. Chop the parsley leaves a little. Cut the chives into rolls. Spread everything over the salad.
Mix the oil and vinegar with salt and pepper. Drizzle the sauce over the salad just before serving.