Preheat the oven to 160'C. In a bowl over a pot of simmering water, melt the dark chocolate and butter

Whisk in the eggs one at a time and add the vanilla essence

Sift in the sugar and flour and fold into the mixture.

Fold in the chopped milk and white chocolate. Pour the mixture out into a greased and lined rectangular baking tray

Bake for 20-25 mins until firm. Remove from the oven and allow to cool slightly before cutting.

Dust with icing sugar and serve plain or with vanilla ice cream