Melt the dark chocolate and stir in 200 ml (0.84 cup)of whipping cream. Put in the fridge for about an hour to cool down.
In another pot, melt the white chocolate with 200ml whipping cream and cool down .
In a third pot, melt milk chocolate with 200ml whipping cream and also cool down.
When the mixture with chocolate are cooled down, mix them with mixer and in the mold place first mixture with dark chocolate, then with milk chocolate and at the top mixture with white chocolate. For decoration you can sprinkle with walnuts.