To Make the Chocolate Mousse Layer: Combine cream cheese, sweetener and milk together in the bowl of a stand mixer, or with a hand mixer. Mix until completely combined. Add cocoa and mix until smooth. Fold in the Tru Whip.
Putting it all together: Place a single layer of cookies in the bottom of a 8x8 inch pan, (you may need to break some cookies up to fit properly). Top cookies with half of the mousse mixture and spread evenly. Repeat layers once, and top with a layer of Tru Whip and chocolate if desired.
Cover the dish and refrigerate overnight or for at least five hours to give the cookies time to soften a bit. When ready to serve, slice and serve immediately.