Preheat oven to 350 degrees. Spray 9" X 13" pan with nonstick spray. In large bowl using hand mixer, beat together the ricotta cheese, eggs, sugar and vanilla until smooth. In another large bowl, mix together your cake mix according to box directions. (The following directions are correct, the layers "switch" during baking time.) Pour cake batter into prepared pan. Spread to fill pan evenly. Once cake batter is in place, carefully pour the cheese mixture evenly over top of cake batter. Spread to cover cake batter as best you can. Bake the cake at 350 degrees for 1 hour, remove and cool completely. Stir pudding mix and milk, whisk till combined, fold in cool whip and spread over cooled cake. Cover and refrigerate at least 6 hours. It tastes even better the next day!!