Clean the mushrooms, cut larger ones in half. Finely chop the onion and garlic.
Then put all the ingredients, except for the parsley, in a saucepan and mix well. Cover and simmer over a mild heat for 3 to 4 hours, stirring occasionally. In a pressure cooker 1.5 to 2 hours.
If necessary, season again with salt, pepper and vinegar and mix in the chopped parsley.
Even if it seems too runny at first, after the cooking time you get a wonderfully creamy and aromatic dish. Fresh baguette tastes best with it.