Prepare the brownie mix in a large bowl following the instructions on the box. Bake, then allow to cool completely.
In a large mixing bowl, beat together cream cheese and powdered sugar with an electric mixer until well combined.
Gently fold whipped topping into the cream cheese mixture.
In a microwave-safe bowl, combine chocolate and butter (cut the butter into small cubes for even melting). Microwave on high for 30 seconds. Stir, then continue microwaving in 15-second increments until the chocolate and butter are fully melted and smooth.
Mix the melted chocolate blend into the cream cheese mix until thoroughly combined.
Once cooled, evenly spread the French silk topping over the top of the brownies. Refrigerate until set, about 2-4 hours.
Cut the set brownies into squares. Optionally, top each square with more whipped cream and chocolate shavings before serving.
Notes
To ensure an even layer of French silk topping, use a spatula or the back of a spoon to smooth it over the brownie base.
For a more intense chocolate flavor, opt for dark chocolate chips instead of milk chocolate chips in the mousse.
If the mousse mixture appears too thick after mixing, a small amount of cream can be folded in to achieve the desired silky texture.
When spreading the chocolate mousse over the brownie base, be gentle to prevent the brownie layer from breaking or mixing into the mousse.
For a professional touch, use a piping bag and star tip to add whipped cream on top of each brownie square before serving.
For those who prefer a crunch, consider adding a layer of finely chopped nuts between the brownie base and the chocolate mousse layer.