250 g flour
150-200 g butter
200 g sugar
1 teaspoon vanilla essence
3 teaspoons baking powder
1/8 teaspoon salt
2 tablespoons cocoa powder / or Nutella
Whisk the egg whites with a little salt until firm, and set aside.
Beat the yolks with sugar, add butter, vanilla and mix well.
Mix the flour with baking powder.
Add flour and egg whites to to the batter (alternating - a couple of spoons of flour, then a couple of spoons of egg whites). Mix everything well, and then divide the batter in two. Leave one half yellow, and add cocoa powder or Nutella to the other half.
In a long cake form, 24x14x8 cm, (greased and floured) put alternatelly yellow and brown mixture.
Bake for 40 mins at 180°C (350 F), or until a toothpick comes out clean.
Pairs Well With
The original recipe is with cocoa powder, but lately, I prefer substituting it with Nutella, it's so much more delicious.
Another possibility is to add white chocolate (chopped) and/or ground hazelnuts to the yellow batter, and dark chocolate chips to the dark part.