Instructions:

Brownie Base:

1. Preheat your oven to 180°C / 350°F. Spray an 8-inch springform pan with oil spray and line the bottom with baking paper.
2. In a heatproof bowl set over a pot of simmering water, melt butter, dark chocolate, and brown sugar until smooth. Remove from heat and whisk in the eggs, followed by the flour until batter is smooth.
3. Pour the batter into the prepared pan and bake for 20 minutes. Once baked, cool completely at room temperature.

Mousse:

1. In a heatproof bowl set over a double boiler, melt milk and dark chocolate until smooth. Remove from heat and stir in egg yolks until mixture thickens.
2. Soak gelatine leaves in cold water for 5 minutes, then dissolve in a jug with 1 cup of heated cream. Stir until melted.
3. Combine the hot cream-gelatine mixture with the chocolate mixture until smooth.
4. In a separate bowl, whip egg whites until soft peaks form. Gradually add sugar and whip until glossy.
5. In another bowl, whip remaining cream and vanilla until stiff peaks form.
6. Gently fold whipped cream into chocolate mixture, followed by whipped egg whites until well combined.
7. Pour the mousse over the cooled brownie base in the springform pan. Chill in the fridge for 4 hours or overnight.
8. To serve, run a knife under hot water and dry. Run it around the top of the mousse layer before loosening it from the springform pan. Gently unwrap it from the acetate and slice.

Savor each luxurious bite of this Chocolate Mousse Cake and delight in its luscious texture and rich chocolate flavor. Perfect for special occasions or anytime you crave a decadent treat!