Preheat oven to 475 degrees and place large pan filled with 1/2 inch of water in the oven.
Use a mixer to mix cream cheese, sugar, sour cream and vanilla. Blend until smooth and creamy. Wisk eggs in a small bowl, then add to cream cheese mixture. Blend only until incorporated.
Pour into a 9 inch Springform pan and place pan in preheated water bath in oven. Bake 12 minutes and turn oven down to 350 degrees. Bake til top becomes golden, about 50-60 minutes. Remove to wire rack to cool and then refrigerate until ready to assemble the cake. Once the cake has cooled,remove the cheesecake from the springform pan and place on a flat surface like a cutting board. Ready the pan for the brownie layer to be baked.
Make the browie base and the chocolate mousse while cheesecake is cooling in the refrigerator.
Preheat the oven to 350 degrees. Spray the springform pan with cooking spray and coat with cocoa.
In a large bowl combine the melted butter and sugar.Add eggs and stir until well combined. Add vanilla and set aside.
In a smaller bowl, combine flour, cocoa, baking powder and salt. Add the flour mixture to the egg mixture and beat unil all the ingredients are wet.
Pour the brownie mixture into the prepared springform pan and bake for 20-25 minutes. Allow the brownie to cool completely in pan and when cool, invert onto a wire cooling rack.
Make the Mousse mixture: in a small bowl, pour gelatin into the cold water and let it stand for a minute or so until it is soft. Add the boiling water and stir until the gelatin is completely disolved and the mixture is clear. Cool slightly.
In a medium bowl, stir together the sugar and cocoa. Add the whipping cream, vanilla and coffee. Using an electric mixer, beat the mixture and scrape the bottom of the bowl occasionally, until the mixture is stiff. Pour in the gelatin mixture and beat until well blended. Place the mousse in the refrigerator until you are ready to assemble the cake.
Assembling the cake: Remove the cheesecake from the board it is set on. Carefully put the brownie base into the springform pan. Gently slide the cheesecake layer from the board onto the brownie base. Pour the chocolate mousse on top of the cheesecake layer. Use a spatula to smooth the top.Release the pan from around these two layers, spread mousse onto the sides creating a smooth surface. Refrigerate at least one hour to enable the layers to beocme firm and not fall apart while serving. Decorate with dollops of whipped cream.