Heat your over to 170°C fan/150°C/Gas mark 3
Grease your 23cm baking tin and line the base with greaseproof paper.
Bring a small pan of water to boiling point then remove from the heat.
Break your dark chocolate into chunks and put into a heatproof bowl that will balance on top of the small saucepan.
Put the bowl with the chocolate on top of the saucepan of just boiled water and allow the heat to gently melt the chocolate.
Melt your butter slowly over a gentle heat in your large saucepan.
Add your brandy, espresso, vanilla essence and sugar.
Mixing continually with a balloon whisk, heat gently until all of the sugar has dissolved.
Add your melted chocolate and mix in thoroughly.
Set aside to cool for about 15 minutes.
Add your egg whites to a bowl, ensure the bowl is completely clean and grease free.
Whisk your egg whites until they form stiff peaks, this will take about 1 minute and 15 seconds in a stand mixer on a high setting. Set aside.
Add your eggs yolks and ground almonds to your cooled chocolate mixture and beat together for about 1 minute on a medium setting.
Add half of the egg whites to the chocolate mixture and gently fold in with a large metal spoon.
Fold in the rest of your egg whites, again do this gently so that you keep plenty of air in the mixture.
Transfer your cake batter to your cake tin.
Bake in the centre of your oven for 50-55 minutes.
Remove from the oven and leave to cool for 15 minutes before transferring to a cooling rack.
Leave to completely cool before adding your topping.