Melt the butter and chocolate. Once they cool, add the sour cream to them, spoon by spoon, while stirring carefully so it doesn't get runny.
Beat the confectionery cream with a mixer until thickened. Add it to the other cream. Next, add the lemon zest, vanilla and coconut flakes. Stir.
Dip each biscuit for a second in the milk.
Smear the bottom of a form with a thin layer of the cream mixture. It's best if it has a removable ring.
Arrange the wet biscuits on top of the cream mixture. Smear with cream and arrange biscuits again. Finish off with cream.
Put the cake in the fridge for 12 hours.
Before taking it out, slide a knife between the form and cake, to separate them. Sprinkle with coconut flakes on the top and sides. You can decorate with pieces of Bounty chocolate bars or Raffaello bonbons.
Quick, easy and most of all - delicious!