Preheat oven to 180 C. Butter an 8" springform tin. Line the base with parchment paper

Run walnuts, oats and 1 tablespoon brown sugar in food processor till ground. Add the clarified butter/ghee and pulse till it all comes together.

Gently press this into the bottom and up the sides of the baking tin to form a base.

Place the egg whites in the bowl of the stand mixer. Add 50g brown sugar, pinch of cream of tartar and beat on high speed to stiff peaks. Reserve in a separate bowl.

Place the egg yolks in the same bowl of the stand mixer. Beat on high speed for 5-7 minutes until thick and mousse like. Add the remaining 50g brown sugar, coffee powder and scraped vanilla bean, and continue to beat for another 3 minutes. Gently stir in the oats flour and baking powder.

Fold in the melted chocolate and water.

Gently fold in the beaten egg whites, beginning with a quarter at a time.

Turn the filling over the walnut base and spread uniformly. Sprinkle over with 1 tbsp brown sugar

Bake for approximately 30 minutes, cool in the pan for another 15-20 minutes

Loosen sides, and leave to cool completely for about 2 hours. The centre will drop/sink

Chill, then top with the mascarpone cream.

Whisk the mascarpone until smooth.

Take 2-3 tbsp and whisk in the salted caramel sauce to loosen, the gently fold this through the remaining mascarpone. Taste and add more sauce if desired.

Top the chilled cake with this, add some salted caramel popcorn if you like.

Slightly warm a little more salted caramel sauce and drizzle over to finish.