Clean the mushrooms and cut larger heads. Heat the olive oil in a pan. Fry the mushrooms and 2 whole cloves of garlic well, stirring constantly. When the mushrooms have turned a nice color, salt and season with pepper. Then deglaze with a good dash of balsamic vinegar and add the washed and finely chopped parsley. Stir everything again. If the mushrooms are too dry, add a little olive oil, season to taste and transfer everything to a bowl that has been rubbed with a clove of garlic.
Let it steep in the refrigerator for at least 4 hours, but do not serve cold.