Preheat the oven to 180°C and grease and line a 23 cm cake tin. In a separate bowl, whip the egg whites until thick and foamy.
Beat the egg yolks with 160 g of the caster sugar until light and fluffy. With the beater on medium speed add the olive oil, a little at a time, as if you were making a mayonnaise.
Change to a low speed and add the dry ingredients, beating until combined. Add the water.
Add the remaining caster sugar and beat gradually until the mixture forms stiff, glossy peaks. Fold the whites gently but quickly into the chocolate mixture.
When well combined, pour into the prepared cake tin and bake for 1 hour or until a cake-tester or skewer inserted in the middle of the cake comes out clean.