Preheat oven to 350 degrees. Spray two 9 inch round cake pans with non-stick cooking spray.
In a large mixing bowl, combine cake mix, diet soda and egg whites. With an electric mixer, beat on low speed for 1 minute. Beat on medium speed for 2 minutes. Divide mixture evenly between the two cake pans. Bake for about 26 minutes or until a toothpick inserted in the center of cake comes out clean. Remove from oven and allow to cool in pan for 10 minutes. Turn out of pans and cool completely on wire rack.
To make filling, combine cream cheese and sugar. Beat on medium speed with an electric mixture until well blended. Fold in Cool Whip and cookies.
Place cake layer on serving plate top-side down. Spread evenly with cream cheese mixture. Place second cake layer on top.
To make glaze, place baking chocolate in a microwave safe bowl and microwave on high for 1 to 2 minutes, stirring every 30 seconds. Blend in margarine. Allow to sit for about 5 minutes for mixture to thicken slightly.
Spoon glaze over top of cake and serve. Refrigerate any remaining cake.
Nutrition Information:
198 Cal., 4.6 g. fat, 0.4 g. fiber
