To prepare a artichoke spinach casserole casseroles recipe, you will first need to prepare your ingredients. You will need: 1 1/2 cups frozen spinach, 1/2 cup shredded Parmesan cheese, 2 tablespoons olive oil, 1 teaspoon kosher salt, and 1 tablespoon melted butter. Preheat the oven to 350 degrees F (180 degrees C) and grease and flour 2 9-inch square baking pans. Set aside. In the bowl of an electric mixer fitted with the paddle attachment, cream together the butter and sour cream until light and fluffy. Gradually beat in the eggs, beating well after each addition. Pour the creamed mixture into the bottom and sides of the prepared baking dishes. Bake for 20 to 25 minutes or until the tops are browned and the center is set. Let stand for 5 minutes before serving.