Lightly grease a 23 cm springform cake tin with the vegetable oil and line with plastic wrap, leaving an overhang for covering the cake. Place a round of baking paper on the base of the tin.

Combine cream, Baileys, vanilla and icing sugar in a bowl and whip until soft peaks have formed. Refrigerate 100 g of cream for topping the cake the following day.

Assemble the cake by placing a thin layer of cream on the bottom of the tin. Top with a layer of biscuits and repeat with cream and biscuits until all the biscuits have been used.

Finish with a layer of cream, cover, and chill overnight.

To serve, remove plastic wrap from the top of the cake. Invert the cake onto a serving platter and remove the tin, plastic wrap and baking paper. Spread the reserved cream on top.

Shave curls of chocolate from each of the chocolate blocks to decorate the top of the cake.