Ensure chocolate mixture is cooled before adding remaining ingredients. Un-iced cake can be made up to one week ahead.
300g unsalted butter, chopped
1 cup water
300g white cooking chocolate, chopped
1 1⁄2 cups caster sugar
2 cups plain our
2/3 cup self-raising our
3 eggs, lightly beaten
1 tsp vanilla extract
1⁄2 cup frozen raspberries
1⁄2 cup frozen blueberries
Fresh raspberries and white chocolate curls, to decorate
300ml tub thickened cream
2 tblsps icing sugar mixture
250g tub mascarpone
Grease a 24cm round cake pan. Line base and side with baking paper, extending paper 3cm above pan edge.
2 Combine butter and water in a large saucepan. Stir over a low heat until butter is melted and mixture is hot. Remove from heat. Add chocolate. Stir until melted. Transfer to a large bowl. Cool.
3 Add sugar to chocolate mixture. Stir until combined.
Add combined sifted ours. Whisk until smooth. Whisk in eggs and vanilla. Fold in frozen berries. Pour into prepared pan.
4 Cook in a slow oven (150C) for about 2 hours, or until a skewer inserted into the centre comes out clean. (Cover loosely with foil during cooking, if top starts to over-brown.) Remove from oven. Cool completely in pan.
5 To make mascarpone cream, beat cream and sugar in a small bowl of an electric mixer until soft peaks form. Fold in mascarpone.
6 Turn out cake onto a cake stand. Spread mascarpone cream over top and side of cake. Decorate with fresh raspberries and white chocolate curls.