Cut the mushrooms, I took the pickled mushrooms. If you take fresh or frozen, respectively, boil and also cut them.
Mix everything in a salad bowl. Add pepper if desired. Make a dressing of vinegar (you can take lemon juice, citric acid), water, salt, sugar and vegetable oil. Pour the salad, let it brew, put a slide, decorate as desired lettuce, any greens (I have cilantro), olives.
To clarify, I took half a teaspoon of acetic acid (70% ) and 50 ml of water for refueling.