
Cut the butter into small pieces and let it soften at room temperature until easily spreadable. If you are short on time, microwave it in very short bursts, checking often so it softens without melting.



Place the softened butter and powdered sugar in a large bowl. Beat or stir until the mixture is smooth, pale, and creamy.



Separate the eggs. Add the yolks to the butter mixture and beat until fully incorporated. Keep the egg whites in a clean, grease-free bowl for whipping later.


Melt the dark chocolate gently in a heatproof bowl set over simmering water, or microwave it in short intervals, stirring between each one. Let it cool slightly, then mix it into the butter, sugar, and egg yolk mixture until glossy and even.



Whip the egg whites until stiff peaks form. Fold them into the chocolate mixture in two or three additions, using slow, lifting motions to keep the cream light. Refrigerate the chocolate cream while you prepare the biscuits.



Choose a rectangular serving dish or tray and test the biscuit layout before assembling. Warm the milk in a shallow bowl, then dip each biscuit briefly, just long enough to soften the surface without making it fall apart.



Arrange a layer of dipped biscuits in the dish. Spread a layer of chocolate cream over the biscuits, then repeat with more dipped biscuits and cream. Continue layering until the ingredients are used, finishing with chocolate cream on top and spreading some around the sides if desired.



Decorate the top with extra melted chocolate, cocoa powder, chocolate shavings, meringues, or a light dusting of powdered sugar. Cover and refrigerate for at least 4 hours, or until the cake is firm enough to slice cleanly.



Serve chilled, slicing with a sharp knife wiped clean between cuts for neat layers.
