Make the Crust

1. Line the bottom of a 9 inch springform pan with aluminum foil, wrapping it around the removable bottom of the pan.
2. To make the crust, combine the melted butter and Oreo crumbs and stir until combined.
3. Add the crumb mixture to the springform pan and press into the bottom in an even layer. Set aside.

Make the Ice Cream Layer

1. Whip the heavy whipping cream and powdered sugar on high speed until stiff peaks form. Set whipped cream aside.
2. Beat cream cheese on medium-high speed for 2-3 minutes until light and fluffy.
3. Slowly add the sugar to the cream cheese while mixing.
4. Add the Irish cream liqueur and vanilla extract and beat until smooth and creamy, scraping down the sides to make sure everything is well combined.
5. Fold the whipped cream into the cream cheese mixture until well combined.
6. Spread the ice cream evenly into the pan over the crust, then set in the freezer.

Make the Mousse Layer

1. Whip the heavy whipping cream, Irish cream liqueur, powdered sugar and cocoa powder on high speed until stiff peaks form.
2. Spread the mousse into an even layer on top of the ice cream.
3. Cover the cake and freeze until firm, 4-6 hours or overnight.

Finish Off the Cake

1. Once cake has set, remove it from the springform pan and place it on a serving plate.
2. Make the whipped cream topping by beating the heavy whipping cream, Irish cream liqueur and powdered sugar on high speed until stiff peaks form.
3. Put the whipped cream in a piping bag fitted with a closed star tip. I used Ateco tip 844, but Wilton 2D or 1M would work as well. Pipe the whipped cream around the outer edge of the cake. 
4. Drizzle the cake with chocolate sauce and chocolate sprinkles if desired. Then freeze until ready to serve. Allow cake to sit out for about 15 minutes before serving.
5. Will keep up to 3 months in the freezer.