1. Prebake quiche dough.
2. Combine eggs, cream and pepper and set aside. Sauté onions in one tablespoon of butter. Stir in mushrooms, salt and lemon juice. Cover pan and cook over low heat for eight minutes.
3. Uncover pan and cook over medium heat until liquid evaporates. Gradually stir in eggs. Pour into shell. Sprinkle cheese. Dot with remaining butter.
4. Bake at 375 degrees Fahrenheit for 30 minutes.