Preheat oven to 170°C (150°C fan-forced). Place a 23cm (approx) round silicone dish (available from the Lyndey Milan range) on a baking tray. Or lightly grease a 23cm round cake tin and line base with baking paper.
Melt the butter in a medium saucepan and add sugar, chocolate and condensed milk. Cook over a low heat, stirring occasionally, until the mixture thickens slightly and the sugar dissolves. Remove from the heat and cool slightly.
Whisk together sour cream and eggs in a large mixing bowl. Add cooled chocolate mixture and flour and mix well. Pour into dish and bake for 45 – 55 minutes or until cooked. Stand in dish for 10 minutes before turning onto a wire rack to cool.
To serve, place cake on serving plate, sieve cocoa over the top of the cake. Add the raspberries and drizzle with the melted white chocolate. Serve with thick cream if desired.
