Flourless Dark Chocolate Cake

Preheat the oven to 190°C / 170°C fan / 375°F / Gas 4.

Roughly chop the dark chocolate.

Tip: A handy tip is to chop it while it’s still on its wrapper, which makes it much easier to transfer without making a mess.

Transfer the chopped chocolate to a medium heatproof bowl and add the butter.

Melt the chocolate and butter together in the microwave in 10-second intervals, stirring well between each one, until completely melted, smooth and glossy. Set aside to cool.

In a separate large bowl, beat the eggs and sugar together until pale, fluffy and approximately doubled in volume.

Using a spatula or large metal spoon, gradually fold the cooled chocolate mixture into the eggs, about 1 tablespoon at a time, taking care not to knock out too much air.

In a separate bowl, mix together the cocoa powder, cornflour, bicarbonate of soda and salt. Sift the dry ingredients over the chocolate and egg mixture, then gently fold until just combined.

Mix together the sour cream, vanilla extract and cooled espresso. Gradually fold this into the batter, about 1 tablespoon at a time. You may not need all of the liquid, so stop adding it if the batter begins to look too runny. The finished batter should be smooth and thick, but still easy to pour.

Generously butter a 9-inch (23 cm) round cake tin, then pour in the batter and spread it evenly.

Scatter the crushed nuts over the top. Using a teaspoon, gently swirl them into the surface of the batter.

Bake in the preheated oven for 20–25 minutes, until the top has formed a delicate crust while the centre remains soft and moist.

Remove from the oven and allow the cake to cool in the tin before serving.