Hazelnutsto taste (roasted and lightly chopped) (optional)
Preheat your oven to 180 ºC and cover a 26-cm round cake pan with some non-stick spray.
Prepare the coffee and, in a medium bowl, pour on the chocolate. Let it rest for a few minutes. Whisk until the chocolate is fully melted and well combined with the coffee. Set aside.
In a large bowl, whisk the butter and the sugar.
Add the egg, the yolks and the vanilla essence, and keep whisking until you get a consistent mix.
With a spatula, fold in half of the flour and then half of the egg whites, already whipped to stiff peaks. Add the coffee and chocolate, and keep folding in the batter. Add the remaining flour and egg whites.
Bake for 40 minutes, or until when you insert a toothpick in the middle, it comes out clean.
Let it cool completely. Spread some Nutella and hazelnuts on top of the cake.
TOP: This cake is delicious on its own, so you can skip the Nutella on top if you want to save on some calories. But let me tell you, they are worth it and it takes the cake to another level.
STORAGE: Store in an air-tight container up to 4 days at room temperature, or for a week in the fridge, or you can easily freeze it.