To prepare a spinach cheese casserole in puff pastry casseroles recipe, you will first need to prepare your ingredients. Preheat the oven to 375 degrees F (190 degrees C) and grease and flour two 9-inch (23.25-centimeter) round baking pans. Set aside. In the bowl of an electric mixer fitted with the paddle attachment, cream together the butter and sugar until light and fluffy. Add the eggs and vanilla and beat until combined. Gradually add the flour mixture and mix until the mixture resembles crumbled breadcrumbs. Fold in the spinach and cheese. Bake for 20 to 25 minutes or until browned and bubbly. Let stand for 5 minutes before serving.