Slice the pound cake into ⅓ to ½-inch slices, then cut each piece in half diagonally from corner to corner to create long triangles.
Fully line the inside of a zuccotto mold or 1 ½ or 2-quart bowl with plastic wrap. Then line the plastic wrap lined bowl with the triangles of pound cake in any design you would like, just be sure to place the pieces tightly together to avoid any gaps. You should have some leftover pieces, you will use these later.
Lightly brush the pound cake that is lining the bowl with amaretto.
In a microwave safe bowl, melt the dark chocolate chips. Set aside to cool down for a few minutes.
While the chocolate is cooling, whip 1 cup of the heavy cream to stiff peaks.
When the chocolate is cool, but still melted, fold ½ of the whipped cream into the melted chocolate. Once it is mostly combined, add the remaining whipped cream and continue to gently fold until combined.
Grate or shave ¾ of the dark chocolate bar into the chocolate mousse mixture, and fold to combine.
Spread the chocolate mousse to cover the pound cake lining the bowl, set in the fridge while you work on the next filling.
Whip the remaining 1 ½ cups of heavy cream with ¼ cup of the powdered sugar to very soft peaks. Set aside.
Whip the mascarpone cheese with the remaining ¼ cup of powdered sugar and 2 tablespoons of the amaretto.
Add the whipped cream to the mascarpone and whip until you achieve stiff peaks.
Reserve about ½ to ¾ cup of the mascarpone whipped cream to use for decorating later.
Fold 2 tablespoons of christmas sprinkles into the mascarpone whipped cream, be very gentle and do not over-mix. This is to prevent the sprinkles from bleeding their color too much.
Take the cake out of the fridge and fill to almost the top with the mascarpone whipped cream.
Use the remaining triangles of pound cake to cover the top of the cream all the way to the edges, closing the filling in. Then brush the top of the pound cake with amaretto.
Cover the cake with plastic wrap, and place in the fridge for 4 hours.
When ready to serve, remove the plastic wrap and invert the cake onto a serving platter. Remove the bowl and any remaining plastic wrap carefully.
Lightly sift the cocoa powder all over the exterior of the cake.
Pipe the remaining mascarpone whipped cream in the circle around the top of the cake dome.
Shave the remaining chocolate bar and fill the inside of the whipped cream circle with the chocolate shavings.
Sprinkle the whipped cream with more Christmas sprinkles.