1. Wash the mushrooms and remove the trunk. Add salt and pepper to taste.
2. Finely chop the garlic, onion and parsley.
3. Bring a frying pan over medium heat, and add a little olive oil.
4. Put the vegetables in the pan and add the lemon juice.
5. Cook for 5 minutes.
6. Stuff the mushrooms and place them on a plate, previously greased.
7. Bake for 10 minutes at 170ºC/340ºF.
8. Check doneness.