1. Peel and chop the onions.
2. Squeeze the lemon and set the juice aside.
3. Chop the parsley (only the leaves).
4. Lay the garlic clove, face down on a chopping board and apply pressure on it, with the flat of a knife, to split the skin. Remove the peel.
5. Chop off the ends of the Garlic clove and dice the remaining portion.
6. Mix some salt with the chopped garlic and mince with the flat of a knife.
7. In a non stick frying skillet, heat some olive oil.
8. Add the onions and fry them on medium heat for 1-2 minutes.
9. Mix the mushrooms with the onions and sprinkle a little salt over them. Cook uncovered for ten minutes.
10. Pour the white wine into the pan and stir well. Cook the alcohol out for 2 minutes.
11. Add the minced garlic to the pan, stir well and cook for 1 minute.
12. Mix in the lemon juice and scatter the chopped parsley, on top of the mushrooms. Cook for 2 minutes.
13. Add a cup of heavy cream to the pan. Continuously stir for 5 minutes, to prevent it from sticking to the base of the pan.
14. Mix some butter into the sauce to thicken it further.
15. Garnish with freshly ground pepper, sprigs of parsley and serve served warm, with your choice of main dish or simply with garlic bread and green salad.