|100 g||all-purpose flour|
|50 g||cocoa powder|
|50 ml||vegetable oil|
|280 g||chocolate (bittersweet)|
|150 g||chocolate (milk)|
|850 ml||whipping cream|
|1 tsp||instant espresso powder (optional)|
Preheat oven to 180°C/350°F. Add part of the eggs and the sugar to a standing mixer. Beat until the color of the mixture is very pale and it has grown in volume. Add lemon zest. Sift flour, cornstarch, cocoa powder, and salt into the mixer bowl. Beat until a smooth dough forms.
Transfer dough to a lined baking sheet and even out surface. Bake in preheated oven at 180°C/350°F for approx. 10 – 15 min. Remove from oven and place on a wet kitchen towel. Carefully remove parchment paper and use the towel to gently roll your cake. This way you prevent the surface from cracking and ensure that you will be able to form a nice cake roll later.
Gently melt chocolate over a water bath over medium heat. Once it has melted, set aside.
Separate part of the eggs. Add yolk as well as remaining eggs to a large bowl. Place bowl on the water bath and whisk eggs until they are thickened.
Beat cream until stiff. Add molten chocolate, orange zest, and instant espresso powder to the eggs and incorporate. Set aside to cool for approx. 10 min. When the mixture has cooled, gently fold whipped cream into chocolate mixture. Transfer to refrigerator and chill for approx. 1 h.