Take the stems off the mushrooms, and put them aside. Rub the mushrooms with 1-2 teaspoons of olive oil, then with a pinch of salt. Put the mushrooms in a baking dish into an oven at about 350 degrees F.

Meanwhile, mince the mushroom stems, zucchini and onion and stir them together in a bowl. Add another teaspoon of olive oil, another pinch of salt and the vinegar or red wine.

Take the mushrooms out of the oven and fill them with the vegetable mixture. Put any extra stuffing on the side to bake separately. Put the dish back in the oven for 20 minutes, or until the mushrooms are soft.