Prepare the Brownie Base:

1. Preheat the oven to 350 degrees F.  Line the bottom a 6-inch springform pan with parchment paper, spray the parchment paper and the lower 1/3rd of the pan and set it aside.
2. In a medium-size bowl, combine the brownie base ingredients and mix until fully incorporated.  Spread the mixture into the pan and bake for 15 minutes.  Once baked, remove the brownie and allow it to cool fully.

Prepare the Mousse Layers:

1. In a small bowl, heat 1/4 cup of heavy cream in the microwave for about 30 seconds or until hot but NOT boiling.  Stir in the espresso powder and cocoa powder.  Place the mixture in the fridge or freezer to cool.
2. In a large bowl, beat the softened cream cheese with the sweetener until light and fluffy and fully combined.  Beat in 1/3 cup of the heavy cream for about 1-2 minutes.
3. Divide the mixture in half and place each half in a separate bowl.  To one bowl, and add 1 tsp of vanilla and beat until incorporated.   To the other bowl add the cooled espresso chocolate cream mixture and beat for about 1 minute.

Assemble the Mousse Cake:

1. Take the cooled brownie and spread the chocolate espresso mousse over the brownie layer.  Smooth the top.  Next, add the vanilla mousse over the chocolate layer and once again, smooth the top.  Place the cake in the fridge for at least 4 hours or overnight in order to firm.
2. Once firm, top with optional chocolate shavings and slice the cake into 8 servings.