01 -
Heat your oven to 180°C/350°F/160°C Fan/gas mark 4. Line the bottom of a 23cm (9-inch) springform pan with baking parchment.
02 -
Warm the chocolate in the microwave or over a water bath. Let the butter dissolve in the heated chocolate mixture.
03 -
Whisk together the 2 whole eggs and 4 yolks with 75 grams (1/3 cup) of caster sugar. Stir in the cooled chocolate, Cointreau, and orange zest if desired.
04 -
In another clean bowl, whip the 4 egg whites until frothy. Slowly mix in the remaining 100 grams (1/2 cup) of sugar and continue beating until soft peaks form.
05 -
Lightly stir some egg whites into the chocolate batter to loosen it. Carefully fold the rest in. Pour the mix into the ready pan.
06 -
Pop it in the oven for 35-40 minutes. It should rise with cracks on top and set in the middle without wobbling. Cool on a rack—the center will drop as it cools.
07 -
Set the cooled cake (in the pan) onto a plate or stand. Remove the pan gently, leaving the sunken middle intact.
08 -
Beat the double cream until fluffy. Mix in vanilla and Cointreau (if using) and keep whipping until it holds its shape but still feels soft.
09 -
Fill the sunken top with whipped cream, spreading out to the edges. Use a tea strainer to dust cocoa powder on top evenly.