• Melt the chocolate in a bowl placed over a pan of hot, but not boiling, water. As soon as the chocolate has melted, remove the bowl from the heat and leave to cool a little.
  150 g dark chocolate
• Grind the pistachios with 50g of the granulated sugar in a coffee grinder or blender until finely ground. Don't worry about the odd chunk though unless you don't like bits in your cake.
  150 g pistachios
• Cream the butter with another 50g of sugar until very pale. Beat in the ground pistachios.
  150 g unsalted butter
• Separate the eggs. Beat the egg yolks into the cream and butter mixture one by one. Stir in the melted chocolate. Don't wash the bowl, you will need it again.
  6 large eggs
• Whisk the egg whites with a pinch of salt in a separate bowl until peaks form. This is made easier if you have electric beaters or a food mixer. Whisk in the remaining 50g of granulated sugar until you have stiff peaks. Fold this into the cake mixture one third at a time.
  1 pinch sea or rock salt
• Spoon mixture into a 23 cm (9 inch) round silicone cake mould or lined tin. Bake for 15 minutes at 190℃ (375℉, Gas 5). Turn the oven down to 180℃ (350℉, Gas 4) and bake for a further 20-25 minutes. Turn out onto a wire rack to cool.

Chocolate Ganache

• Melt the dark chocolate in a bowl over hot water with the cream and fruit liqueur (I used homemade sea buckthorn liqueur). Stir together lightly with a small whisk to avoid the mixture splitting.
  50 g dark chocolate, 50 ml double cream (heavy cream), 2 tsp fruit liqueur of your choice
• Spread on top of the cooled cake. Scatter with a few chopped pistachios.