For the chocolate sauce, boil 6 tbsp. water, 50 g sugar and 1 pinch of salt in a pot. Stir in the cocoa powder with a whisk. Let everything boil for about 5 minutes while stirring constantly. Remove from heat and stir in 50 g cream. Let it cool down.
Mix mascarpone, vanillin sugar and 40 g sugar. Whip 200 g whipped cream until stiff and fold into the mascarpone in 2 portions. Bring 700 ml milk to the boil. Stir pudding powder, 6 tbsp. sugar and 100 ml milk until smooth. Stir into the boiling milk, bring to the boil and simmer for 1 minute. Remove from the stove.
Line a square springform pan (approx. 24 x 24 cm) with a layer of biscuits. Remove 4 tablespoons of pudding. Spread half the pudding on the cookies and smooth it down. Sprinkle with 1 packet of cream firming agent. Spread half of the mascarpone cream on top. Sprinkle with 4 tbsp. chocolate sauce. Spread one layer of biscuits, the remaining half of the pudding, cream thickener and mascarpone on each. Finish with the remaining biscuits, except 4 pieces, the remaining pudding and 4 tbsp. sauce. Chill the cake overnight.
Cut the chocolate bars into thin slices. Break the remaining biscuits into pieces. Remove the cake from the tin, cut it into pieces (approx. 6 x 7 cm) and sprinkle with cookie pieces and chocolate bar slices.