200 grams plain, sweet biscuits (I used Anzac biscuits)
1⁄4 cup melted butter
375 grams dark chocolate, 72% cocoa
2 cups cream
3 tablespoons rum or other liqueur*
1 teaspoon vanilla extract
icing sugar for sifting
Grease a 20 cm x 5 cm deep, square cake tin and fully line with baking paper, letting it come 1 cm above the rim of the tin. This makes it easier to remove for serving. Roughly break up the biscuits and place in a food processor. Process until finely ground. Take out 4 tablespoons of crumbs and set aside. Add the butter and pulse to combine. Press firmly into the base of the tin to make an even layer. Refrigerate while making the filling.
Filling: Finely chop the chocolate and place in a heat-proof bowl. Heat 3⁄4 cup of the cream to boiling point in a small saucepan and pour over the chocolate. Stir until melted and smooth. Set aside for 5 minutes to cool.
Beat the remaining cream, rum and vanilla to soft peaks. Using a large metal spoon, gently fold into the chocolate until there are no white streaks of cream left.
Pour the mixture over the crumbs and tap the tin gently on the bench to remove any air pockets. Sprinkle the top with the reserved crumbs. Cover tightly with plastic wrap and refrigerate for at least 6 hours or up to 3 days.
To serve: Using the baking paper, lift the cake from the tin and place on a chopping board.
Using a long, sharp knife dipped in hot water, cut into 5 cm squares. Wipe the knife clean and re-warm between each cut. Use a pallet knife to transfer to serving plates. Serve chilled with a spoonful of mascarpone and a small stack of raspberries. The cake will cut into 16 x 5 cm squares.
Other flavours that go with chocolate are brandy, whisky, mint, coffee, orange and most nut liqueurs.