Snowy Mountains Cake

Ingredients
10 1/2 oz good-quality dark chocolate, roughly chopped
4 oz unsalted butter
5 eggs, separated
10 oz caster sugar
1 tsp vanilla extract
1 tbs rum or brandy
1 1/2 tbs cocoa powder, sifted, plus extra to dust
1/4 tsp cream of tartar
1 1/4 cup thickened cream, whipped

Directions:
Preheat the oven to 400 F . Grease a 9 inch springform pan.
Place the chopped chocolate and butter in a heatproof bowl over a saucepan of simmering water (don't let the bowl touch the water). When the chocolate and butter have melted, remove the bowl from the pan and stir the chocolate and butter gently until smooth. Set aside to cool slightly.
Using electric beaters, cream the egg yolks and sugar in a bowl until pale and thick. Add the vanilla extract, rum or brandy and cocoa, then fold in the chocolate mixture using a metal spoon.
In a separate bowl, whisk the eggwhites until soft peaks form. Add the cream of tartar and continue to whisk until stiff peaks form. Fold a little of the eggwhite mixture into the chocolate mixture, then fold in the rest.
Spoon the mixture into the prepared cake pan, then place in the oven and bake for 35-40 minutes until the cake is firm on the outside (it should still be gooey in the centre).
Remove from the oven (the cake will deflate and crack slightly, but the cream topping will cover it) and set aside in the pan to cool. Transfer the cake to a serving platter and fill the centre with whipped cream, making little peaks to resemble snow-capped mountains. Dust with a little extra cocoa to serve.