Melt the Dark Chocolate and Butter together and set aside to cool down.
In a seperate bowl, whisk the Eggs and Brown Sugar until frothy. Sift in then stir the Plain Flour, Baking Powder and Salt.
Add the Melted Chocolate and Butter, then the Milk (optionally with 1 tbsp. Instant Coffee Powder melted in the milk). Quickly stir until combined, then pour into a round Springform Pan.
Bake for 15 to 20 minutes, or until the tip of a knife comes out clean. Set aside to cool down completely.
Chocolate Bavarois Cream
Place the Milk into a medium-size Pot and slowly heat it up. In the meantime, whisk the Egg Yolks and Sugar in a seperate heat-proof bowl.
When the milk starts to boil, directly remove from the heat. Pour it over the Egg Yolks and Sugar while constantly whisking. When combined, transfer back into the pot on the stove.
Add the Dark Chocolate and gently stir until fully melted (Make sure the heat is not too high to avoid burning the chocolate). When the cream starts to boil, add the Agar Agar Powder and whisk for one minute before removing from the heat and into a clean heat-proof bowl. Set aside to cool.See note 1 if you want to use Gelatine instead of Agar, but note that it is a theoretical process as I have not tried it myself.
Place your Heavy/Thickened Cream in the bowl of your mixer, and whisk until you achieve a stiff whipped cream.
Pour the cool Chocolate cream over the whipped cream and gently fold with a silicone spatula. If the whipped cream seem to melt because your chocolate is still too warm, don't worry - it will set again in the fridge.
Pour the Chocolate Bavarian Cream over the Chocolate Brownie Base and place in the fridge to set for 3 hours at least. Keep in the fridge for up to 3 days.
Please note that I have NOT tried this recipe with Gelatine myself. This is a general equivalent measurement, but you may need to experiment a little bit to get the perfect consistency. Gelatine Powder can be used instead of Agar Agar Powder. The general ration of gelatine powder to agar agar powder is 3:1. For this recipe, dissolve 4 1/2 teaspoons of Gelatine Powder in about 60 ml / 1/4 cup of cold water and let it set for about 10 minutes. Follow the rest of the recipe until the Chocolate has melted into the Creme Anglaise base. Transfer the Chocolate cream into a heat-proof bowl and leave to cool down for 5 minutes, then add the Gelatine. Whisk well and set aside to cool down completely before folding in the Whipped Cream.
Recipe provided by "A Baking Journey" - https://www.abakingjourney.com