Melt the dark chocolate and the margarine (or butter) in the microwave. Set aside to cool a little
Whisk the eggs and sugar together on a high speed electric whisk for a couple of minutes until doubled in volume
Fold in the sifted flour and cocoa powder, melted chocolate and the chopped up white and milk chocolate (or chocolate buttons if you are lazy like me!).
Place in a greased 20cm by 20cm brownie tray or square tin
Bake at 180 degrees/gas 4 for 25 mins until just set