Preheat fan oven to 160˚C (325˚F) or 175˚C (350˚F) if you're not using a fan oven. Grease and line the bottom of a 9 inch (23 cm) round cake tin with parchment paper. Set aside.
Over a pot of simmering water, melt together chocolate (cut into chunks) and butter, stirring with a silicone spatula to combine them. When it's done, leave aside to cool a little bit.
Separate eggs into yolks and whites. Using a hand or a stand mixer, beat the yolks with sugar and vanilla for 5-6 minutes, or until the mixture becomes voluminous, pale and silky.
In another bowl, mix egg whites with salt until you get stiff peaks. Be careful, because it's easy to overmix the egg whites when there is no sugar involved.
Add cooled chocolate/butter mixture to the egg yolks and carefully fold everything with a silicone spatula or a metal spoon. Since there is no raising agents in this recipe, we rely solely on the eggs and air beaten into them. Make sure everything is nicely combined and there are no egg yolk streaks in the mixture.
Next, fold in the almond flour, until everything combines.
Lastly, add the egg whites -- but add them in batches, so you don't knock the air out.
Pour the batter into a prepared tin and bake in a preheated oven for 40-50 minutes.* The cake is done when you poke a skewer in the middle and it comes out with just a few crumbs.
Once the cake is done, let it slowly cool in the pan on a wire rack for 10-15 minutes, before removing from the pan to cool completely.
for the irish cream mascarpone frosting
In a bowl of a standing mixer, beat cold mascarpone with powdered sugar until creamy. Add cold heavy cream and beat until everything is combined and creamy, soft peaks. Then add 4-5 tablespoons of Irish cream liqueur (more or less to your liking) and fold it with a silicone spatula, so you don't overmix the frosting.
*Not all ovens are the same. I suggest to check the cake at 35 min mark and then adjust the baking time accordingly. Get to know your oven! ?
If you still don’t own one, I advise you to buy a kitchen scale – they’re cheap and easy to use, and always guarantee the same results in baking! ?
Keep the cake in the fridge, because of the dairy frosting. Since it's really moist, it won't dry out, just make sure to cover in plastic wrap to avoid fridge odours.