Preheat oven to 350°F Spray an 9-inch springform pan with vegetable spray.
Wash spinash and shake off excess water. In the water clinging to the leaves, cook the spinach over high heat just until it wilts. Squeeze out excess moisture, chop and set aside.
In large nonstick skillet, heat oil over medium heat; add garlic, onions and mushrooms and cook for 5 minutes or until softened. Remove from heat and add chopped spinach, ricotta, cottage, Cheddar and Parmesan cheeses, whole egg, egg white, dill and pepper; mix well.
Pour into prepared pan and bake for 35 to 40 minutes or until knife inserted in center comes out clean.