Whip mascarpone cheese in a separate bowl, set aside. In another bowl, take whipping cream and icing sugar together and whip for 2-3 minutes, till it reaches soft peaks. Now sprinkle sugar, whiskey and coffee powder and whip them together till it reaches stiff peak for 4-5 minutes. Gently fold in coffee whipped cream into mascarpone. Spread on top of the cake and decorate with chocolate shavings.
Notes
You need to add icing sugar only if you are using mascarpone or cream cheese in whipping cream. Else the whipping cream is sweet in itself.
You can replace whiskey with any other liquor of your choice or even skip it.