Step 1

Prepare the Oven and Tin: Preheat the oven to 180°C/350ºF/160°C Fan/gas mark Line the bottom of a 23cm (9-inch) springform cake tin with baking parchment.

Step 2

Melt the Chocolate and Butter: Melt the dark chocolate either in a double boiler or microwave, then allow the butter to melt in the warm chocolate.

Step 3

Mix the Eggs and Sugar: Beat the 2 whole eggs and 4 egg yolks with 75g (1/3 cup) of the caster sugar, then gently mix in the melted chocolate, Cointreau, and orange zest.

Step 4

Whisk the Egg Whites: In a separate bowl, whisk the 4 egg whites until foamy, gradually adding the remaining 100g (1/2 cup) of sugar. Whisk until the egg whites hold their shape, but are not too stiff.

Step 5

Combine the Mixtures: Lighten the chocolate mixture with a dollop of egg whites, then fold in the remaining egg whites. Pour the mixture into the prepared tin and bake for 35-40 minutes, or until the cake is risen, cracked, and the center is no longer wobbly. Let the cake cool in the tin on a wire rack—don’t worry, the middle will sink as it cools.

Step 6

Remove from Tin and Set Up: Once the cake has cooled, place it on a cake stand or plate, still in the tin, and carefully remove the tin. The cracks and rough edges are intentional for a crater-like appearance!

Step 7

Whip the Cream: Whip the double cream until soft, then add the vanilla and Cointreau (if using). Continue whisking until the cream is firm but not stiff.

Step 8

Assemble the Cake: Fill the crater of the cake with the whipped cream, gently easing it toward the edges. Dust the top with cocoa powder using a tea strainer for a light sprinkle.