In large skillet, sauté the mushrooms in butter. Add the onion to rehydrate.
Add spinach and ham. Cook and stir until excess moisture is evaporated. Cool slightly.
Beat eggs. Add cheese and mix well.
Stir in spinach mixture and pepper. Blend together well.
Spread evenly into a greased 9-inch pie plate or quiche dish. Bake 350°F for 40-45 minutes or when a knife that is inserted near center comes out clean. Yield: 6-8 servings.