1. Sift the two cups of flour and set aside.

2. Leave the butter at room temperature for 1 hour until it is soft.

3. Whip the sugar and softened butter until white and creamy.

4. Stir in the eggs, one by one. Add a pinch of salt and the vanilla.

5. Separate the mixture into two equal portions.

6. In the first mixture, fold in a cup of flour, the cornstarch and a tablespoon of baking powder.

7. In the second mixture, fold in the other cup of flour, the cocoa powder, and the other teaspoon of baking powder.

8. In a cake mould, line up a piece of wax paper.

9. Pour the chocolate mixture on the bottom of the cake mould, then pour the vanilla mixture on top of the chocolate mixture.

10. Spread equally, and use a spoon to run through the mixture to obtain a marble effect.

11. Bake at 425 degrees Farenheit, reducing the heat to 375 degrees for 30 minutes.

12. Check the baking process with the help of a knife.

13. Dip the knife into the cake, and if the knife does not come out clean and dry, then further baking is needed.

14. Cool on a wire rack, and slice into 8 equal portions.