Separate egg whites and yolks. In a large bowl, whisk half of the sugar and the egg whites with the electric mixer until fluffy.
60 ml hot water
In a different bowl, mix the other half of the sugar and egg yolks and then add hot water and whisk until the yolks increase in size.
3 eggs, 150 g sugar
Now, add the flour mixture to the egg yolks and stir using a spatula until combined.
Add in the oil, and mix until combined. Finally, Fold the mixture into the egg whites mixture gently until thoroughly combined.
60 ml sunflower oil
Distribute the batter between the prepared baking pans and bake in the preheated oven for 40-45 minutes.
Make the chocolate frosting: In a mixing bowl, whip the whipped cream until stiff peak forms, then add the Nutella and the mascarpone cheese and mix with a spatula until combined.
250 g mascarpone, 4 tablespoon Nutella, 600 ml whipping cream
Assemble the cake: Put the chocolate frosting in a piping bag with your favorite tip.
Put the first chiffon cake layer on a serving plate. Pip the whipped cream to cover the first layer.
Add the second chiffon layer and repeat. Add the top layer and spread the remaining frosting with a spatula. Dust the top layer with cacao powder, pip some swirls of whipped cream on top to decorate, and then refrigerate for 1-2 hours.
1 teaspoon cacao powder
Notes
Make sure to sift your dry ingredients. This minimizes the clumps you have in your batter and makes for a smooth batter.
Allow your chiffon to cool completely before taking them out of the pan and stacking them into layers. Taking them out of the pan while they are too hot will lead to crumbling.