A day ahead
Preheat the oven to 170 °C (gas mark 3). Prepare the chocolate paste.
Break 5 eggs, separating the whites from the yolks. Beat the egg whites with 40 g caster sugar into stiff peaks.
Mix the ground almonds with the icing sugar, then add the flour & cocoa. Carefully fold in the egg whites using a spatula. Grease the tins.
Line them with a layer of chocolate paste 1 cm thick.
Dust with flaked almonds. Bake in the oven for 40 min.
Leave the biscuits to cool on a wire rack. Prepare the pistachio cream. Heat the pistachios in 1 (espresso) cup of milk.
When blanched, remove with a skimming ladle and crush.
Heat the rest of the milk. Remove from the heat as soon as it reaches boiling point. Beat one whole egg in a pan. Gradually add the rest of the caster sugar (70 g), cornflour, and finally the vanilla extract (reserve 1 drop for the chocolate sauce). Pour on the boiling milk, stirring constantly. Reheat gently, stirring constantly to produce a smooth cream. Remove from the heat immediately it reaches boiling point. Stir in the pistachios. Add the butter. Mix to a smooth cream. Assemble the cake. Spread the pistachio cream along the first biscuit. Very carefully, place the second biscuit on top. Cover the cake in cling film to soak up the cream. Refrigerate for at least 12 hours.

On the day
Prepare the chocolate sauce. Break the chocolate into small pieces and melt using a bain-marie. Add the pinch of cinnamon and 1 drop of vanilla extract. Stir in the almond liqueur. Mix well and leave to cool.

Just before serving cut the cake into thick slices using an electric knife. Arrange one slice on each plate. Serve the chocolate sauce separately.

Tip
You can stack several layers of chocolate biscuit and pistachio cream.