Preheat your oven to 150ºC.

Separate the egg whites from the egg yolks

Beat the egg yolks with the sugar until the mixture whitens. Add the melted chocolate, the melted butter and finally and progressively the flour. Blend until well combined.

In a clean bowl, whisk the egg whites with a pinch of salt until stiff peaks form and gently fold into the chocolate mixture.

Pour the mixture into a buttered cake tin.

Bake for 25 to 30 minutes or until a cake-tester/knife comes out clean.