American chocolate brownies

Preheat the oven to 190 ºC and spray a 23 cm square cake tin with non-stick spray and line with baking paper.
Melt the chocolate in a glass bowl over a saucepan with boiling water or in the microwave oven, stirring occasionally.
Cool slightly.
Pour half a cup (125 ml) boiling water over the prunes and soak for a few minutes until soft.
Drain and process in a food-processor.
Beat the prune puree, egg whites, sugar, salt, milk and vanilla essence until well blended and stir in the melted chocolate.
Sift the cake flour and cocoa over the mixture and mix until smooth.
Turn into the prepared cake tin, spreading evenly.
Sprinkle the chocolate chips on top, if using, and bake for 30-35 minutes until done and a testing skewer comes out clean.
Cut the brownies into squares and dust with icing sugar before serving.