Preheat oven to 350 degrees. In a 9- or 10-inch nonstick heat-proof skillet, heat oil over medium heat. Add mushrooms; saute until browned. Using a slotted spoon, transfer mushrooms to a plate lined with paper toweling. Reserve oil in pan.

In a medium bowl, whisk the eggs, water and salt.

Stir in olives, pepperoni, cheese, pepper and cooked mushrooms.

Reheat skillet over low heat. Pour in egg mixture. Cover and cook until eggs are set around edges, but center is still loose, about 8 minutes. Using a rubber spatula, gently loosen egg mixture from sides of pan.

Place skillet in preheated oven and bake, uncovered for 12-15 minutes,or until a knife inserted in center comes out clean.

Transfer frittata to wire rack; let stand 2 minutes. To loosen frittata from pan, slip a rubber spatula between the frittata and skillet. Slide eggs in one piece onto a plate.

Sprinkle with Parmesan cheese and serve immediately.

HINT: If skillet has a plastic or wooden handle, wrap it in foil before placing in oven.