Calamari Sauce

2 medium onions, chopped
5 tablespoons olive oil
2 cloves garlic, crushed
3 cups white wine
1 cup canned plum tomatoes, puréed with the juice
1/2 cup chopped fresh parsley
1 teaspoon oregano
Salt, to taste
Freshly-ground pepper, to taste
4 pounds small calamari, cleaned and sliced crosswise into rings
1 pound fresh mushrooms, sliced

In a heavy skillet sauté onions in olive oil until golden. Add garlic and wine and boil for 3 minutes to let the alcohol evaporate. Add tomato purée, parsley, oregano, salt and pepper. Add calamari; cover and cook over medium heat for about 45 minutes, stirring frequently. Add mushrooms about 5 minutes before serving.