Suzanne's Famous Spinach Quiche

Ingredients

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