1. Preheat oven to 180°C/350°F/Gas 4. Lightly grease and line a 20cms/8"squre tin. An oblong 15cms/6" x 25cms/10" tin also be used!
2. Put half the plain chocolate and butter into a bowl and microwave on ۪high۪, stirring every 30 seconds until chocolate is melted (1 to 2 minutes) Stir until smooth.
3. Beat eggs and sugar together until thick and smooth. Add the melted chocolate mixture and continue beating for about a minute.
4. Stir in flour and remaining chocolate until just mixed.
5. Transfer to prepared tin and bake for about 20 minutes or until edges are set۪ and centre appears soft. DO NOT OVERBAKE.
6. Remove from oven and allow to cool. Cut into squares.

Note:

Square may be dusted with icing sugar or spread with chocolate spread before serving!