Preparation:
1. In a bowl, whisk together milk, oil, flour and egg yolks. Divide into two portions and add cocoa powder to the second portion.
2. In another bowl, beat egg whites with salt, lemon juice and sugar.
3. Divide white and dark mixtures into two portions.
4. Transfer to a baking sheet, add dark mixture, top with white mixture and sprinkle with chocolate chips.
5. Bake in hot water at 170°C (340°F) for 1 hour.

Enjoy your food !