Heat the over to 108C/ 350F/Gas 4

To make the sponge, break up the chocolate and melt very gently with the butter. Remove the bowl from the heat and leave to cool until needed.

Break the eggs into the bowl of a food mixer. Add the sugar and orange zest. Using the whisk attachment, whisk on full power for about 4 minutes or until the mixture is extremely thick and foamy. It's ready when the whisk leaves a ribbon like trail of mixture when you lift it out of the mixture. Gently stir the chocolate mixture then whisk it briefly into the egg mixture. Turn off the power as soon as it is combined to avoid over-mixing. Add the flour and gently fold in using a large metal spoon. Divide the mixture between the two tins and spread evenly.

Bake in heated oven for 20 minutes until a light golden brown and the sponges spring back when gently pressed. Run a round-bladed knife around the inside of the tins, just to loosen the sponges, turn out onto a wire rack and leave to cool completely.

To make the filling, wipe the strawberries and save half of the good-looking ones for decoration. Thickly slice the rest into a bowl. Add the orange zest and juice and the sugar and mix gently. Leave for 10 minutes for the flavours to develop. Grate the white chocolate and gently fold half into the whipped cream. Save the rest for decoration.

To assemble, set one sponge on a serving plate and spoon on the strawberries and juice. Cover with the chocolate cream then top with the second sponge. Decorate with the reserved strawberries and grated chocoalte and dust with icing sugar. Serve

The assembled cake can be stored in an airtight container in the fridge for 24 hours