To make the sponge:

1. Preheat oven to 170C (340F, gas mark 4). Line a bottom of a 23cm (9inch) spring form tin with non-stick baking paper. Do not grease sides.
2. Separate eggs making sure to keep the yolks intact. Place egg whites in a bowl of a mixer and beat on high speed until the whites become frothy and start to form soft peaks, about 2 minutes. Begin adding sugar, a tablespoon at a time while continuing to mix on high speed. The mixture should now be quite firm and glossy. Continue beating on high speed. Whisk yolks and add a tablespoon at a time to the whites until all are incorporated.
3. Reduce mixer speed to very slow. In a separate bowl mix together the flours and add in in three batches. Mix on low speed until just incorporated.
4. Pour batter into prepared tin and bake for 25 minutes. Remove from oven (leave oven on for the strawberries) and cool in the tin completely before removing from tin. To do so, run a knife around the edge of the cake. Using a bread knife, slice the sponge in to two layers.

To make the Strawberry Mousse, once the cake has cooled:

1. Wash and hull strawberries. Cut in half and place on a baking tray lined with baking paper. Roast for 10 minutes at 170C (340F, gas mark 4). Remove from oven and transfer to a blender. Process until smooth. Pour pureed strawberries onto a fine mesh sieve set over a clean bowl and strain, pressing with a spoon. Discard seeds. Add lime juice, zest and milled sugar, whisk to combine. In a small bowl combine gelatine and boiling hot water. Mix until gelatine is dissolved. Add gelatine to the warm strawberry puree. Whisk well before adding yoghurt and whisking again. In a bowl of an electric mixer, whip cream until stiff peaks form. Reduce speed to low and mix in the puree.

To assemble the cake:

1. Place the bottom half of the sponge cake back in the springform tin. Pour in the strawberry mousse, spread evenly and top with the remaining cake layer. Press down gently. Place in the fridge for at least 2 hours to set.

To make the Whipped Vanilla Bean Frosting:

1. In a bowl of an electric mixer, whip cream, sugar and vanilla until stiff peaks form.

To frost and decorate the cake:

1. Run a knife around the edge of the cake to separate the mousse from the sides of the tin. Remove the ring and transfer the cake, gently, to a serving platter. Place half of the frosting on the top of the cake and spread. Using a knife, Spread remaining icing around the sides of the cake, rustic is fine. Top the cake with coconut flakes and rose petals.