• Grease the sides of the pan to prevent the chocolate cake from sticking.

Prepare the dry caramel :

• Pour the sugar into a saucepan over medium heat. Leave the sugar to melt without stirring it.
• Stir the saucepan from time to time, lifting it from the heat. The sugar will start to caramelize.
• When the sugar has almost completely melted, stir with a whisk or wooden spoon to melt any stubborn pieces of  sugar. Remove it from the heat when it has reached a nice amber color.
• You can deglaze it with a tablespoon of hot water, but it's not necessary. Pour the water in and immediately cover the pot with a lid to avoid splattering.
• Immediately pour the caramel into the bottom of the mold, moving it around to evenly spread the caramel Set it aside.

Flan custard mixture :

• Preheat oven to 150°C (300°F), conventional oven.
• In a mixing bowl, lightly whisk the whole eggs and egg yolks with the sugar and vanilla. Don't try to whiten the mixture. If you're using vanilla beans, cut them in half, scrape out the seeds and infuse in hot milk for 15 minutes or more before starting.
• Add the cold or hot milk to the mixture, stirring as you go.
• Strain and set aside.

Moist chocolate cake :

• Cream the butter with the sugar and add the eggs one at a time, whisking continuously.
• Add the milk while continuing to mix, then sift the cocoa, flour, and baking powder on top. You can sift them together beforehand.
• Whisk well to smooth the batter.
• Place the pan in a large dish with high edges (for the water bath).
• Pour the flan mixture over the caramel, then pour the cake batter over it in the center.
• You can reverse the process, pouring the chocolate batter over the caramel first, then pouring the flan mixture over it. The result will be the same.
• Place the dish on the rack in the middle of the oven and fill with hot water to a height of 2 cm / 0.8 inch.
• In the video, I filled the dish with hot water before putting it in the oven. It was somehow risky to move it. I proceeded this way to shoot the video.
• Bake for about 1 hour. Check the doneness by inserting a skewer into the center of the chocoflan It must come out dry. The cake on top is firm and doesn't move.
• Remove the cake pan from the oven and run a tiny knife blade or skewer around the edge to unstick the cake a little bit. This will prevent cracks.
• Let it cool for 2 hours at room temperature, then refrigerate Let it cool for at least 4 hours before unmolding. I prefer to prepare it the day before so that it can be unmolded easily the next day. It will be well chilled and firm.
• Turn out onto a plate, preferably let it to come to room temperature before serving. The chocolate cake will be softer and more melting in the mouth.
• I removed the caramel that dripped onto the plate just by tilting it and holding the flan with my hand. If you like a pretty visual impression, like an entremet on the plate, do it just before serving.
• Indeed, to preserve the softness of the chocolate cake, it's best to leave it in the caramel.
• As you can see, there's nothing "impossible "about this cake. I guarantee you it's super delicious.