Blitz your biscuits in a food processor, or bash them up as finely as you can. Add in your cocoa powder if using and blitz again.
Mix in the melted butter, and press down firmly into the bottom of an 8"/20cm deep springform tin.
Leave to set in the fridge whilst you do the rest.
Cheesecake Filling
In a stand mixer, add your mascarpone and icing sugar and whisk until smooth.
Add in your double cream and Baileys and whisk again until thick and combined. It doesn't take that long at all, and it's better to be slightly under whisked than over whisked.
If thick enough, it should still be smooth, but hold itself. So check often to see if its thick enough.
Add onto your biscuit base and smooth it over. Chill in the fridge for 5-6 hours, or preferably overnight.
Decoration
Whip up the double cream and the icing sugar to soft peaks.
Melt your dark chocolate, and drizzle over the cheesecake.
Pipe the cream around the edges, and sprinkle on your favourite sprinkles!
Notes
I used the new Baileys Original, but you can easily use the strawberry one, chocolate one, or even try the almond one, etc!
If you are unsure if it has set correctly, you can add in gelatine to help it set. Use packet instructions to do this.
The cream on top is optional, but I think it looks pretty!
If you're worried its not set properly, you can freeze it for an hour or so before serving!