Prepare a round baking pan (diameter 8 in and 3 in depth). Grease with butter then line the base and the side with parchment paper.

Prepare another larger round/square pan. Fill with water to 1/3 the height of the pan. Put this pan in the oven while preheat the oven to 340°F.

Sift flour, cornstarch and salt. In a bowl, stir egg yolks, whole eggs, oil, milk and vanilla. Mix them well. Add the flour mixture. Stir until well blended. Put aside.

Beat the egg whites on low speed until foamy. Then, add the sugar in 3 batches. Beat on medium or medium high until soft peaks form.

With a spatula, fold in the meringue into the egg yolks mixture in 3-4 batches.

Divide the mixture into 2 equal parts, Add chocolate paste to the first part, mix well.
Pour 1/4 cup of white batter in the middle of the pan, then alternately each color.

Carefully put the pan inside the other pan which filled with water (from the oven). Put them all back to the oven. Bake for 50-55 minutes. Test with skewer to see it it's done. The skewer should come out clean.

Once cooked, remove it from the oven, leave it for a few minutes then take the cake out from the pan. Leave it on the wire rack until it gets cool.

Store in a covered container in room temperature up to 3 days (if it lasts that long 😁).