Preheat your oven to 350°F (175°C) and grease a 9x13-inch baking pan. Prepare the brownie mix according to the package instructions, incorporating the extra-large egg. Pour the batter into the prepared pan and bake for 25–30 minutes or until a toothpick inserted comes out clean. Allow to cool completely.

While the brownies cool, beat the softened cream cheese and powdered sugar together until smooth. Fold in one container of thawed Cool Whip and spread evenly over the cooled brownie.

In another bowl, whisk together the instant chocolate pudding mix and instant vanilla pudding mix with 3.5 cups of cold milk for about 2 minutes until thickened. Pour this mixture over the cream cheese layer, spreading evenly.

Spread the second container of thawed Cool Whip over the pudding layer to create a smooth, even layer.

Garnish with chocolate shavings or a drizzle of chocolate syrup. Cover with plastic wrap and refrigerate for at least 4 hours or overnight.