Difficulty:[usr 2]
Crack the eggs, separating the whites from the yolks.
Put the yolks in a bowl with the powdered sugar. Whisk until the mixture whitens and forms a ribbon when the whisk is lifted.
Add the cocoa while continuing to whisk.
Mix the flour, cornstarch and baking powder and add them while stirring with a wooden spoon.
Melt the butter in a saucepan over very low heat, then pour it into the bowl and mix.
Beat the egg whites until stiff with the pinch of salt. Gently fold them into the cocoa mixture.
Pour the mixture into a buttered and floured mold.
Bake for 40 minutes in a preheated oven (180°, th. 6). At the end of cooking, the blade of a knife planted in the dough should come out very lightly coated.
Leave to cool before unmolding and sprinkle with icing sugar.
