1 (9 inch) unbaked pie crust
1 (10 ounce) package frozen chopped spinach
2 eggs
1 cup plain yogurt
1 tablespoon all-purpose flour
1/4 teaspoon black pepper
4 1/2 ounces fresh mushrooms, thinly sliced
4 ounces shredded Cheddar cheese
1/4 cup chopped green onions