Heat oven to 375 degrees F. Spray 12-cup fluted tube pan with cooking spray; pour in chocolate syrup.

Beat cake mix, water, oil, and 3 eggs with mixer 2 minutes or until well blended; blend in sour cream. Pour over syrup in pan.

Beat cream cheese and sugar with mixer until well blended. Add remaining eggs; mix well. Blend in evaporated milk and melted chocolate; gently spoon over cake batter in pan. Cover with foil sprayed with cooking spray, sprayed-side down.

Place tube pan in shallow pan. Add enough water to larger pan to come at least 2 inches up side of tube pan. Bake 1 hour 30 minutes or until toothpick inserted near center comes out clean. Cool completely in pan on wire rack. Refrigerate 2 hours. Invert cake onto plate; remove pan. Serve cake topped with COOL WHIP.

Size-Wise: Since this layered chocolate cake makes 24 servings, it's the perfect dessert to serve at your next party.

Note: The cream cheese mixture sinks to the bottom of the cake batter in pan as the cake bakes, forming the mousse layer at the top of the unmolded cake. To unmold cooled cake, use long thin spatula to loosen cake from side of pan. Place plate over cake pan; invert cake onto plate. Gently remove pan. Spoon any chocolate syrup remaining in pan over cake.

Important Note: To prevent overflow, check cake pan to confirm it is the required 12-cup size. Just measure 3 quarts (12 cups) water and pour into empty pan to verify the volume before using as directed. If you only have a 10-cup fluted tube pan, reserve 2 cups cake batter before pouring remaining batter into prepared tube pan. Continue as directed. Reserved cake batter will make 9 cupcakes. Bake as directed on cake mix package.