Pre heat oven to 170 c ( 325 F) gas 3 . Line a baking tray 33x 23 x 5cm with greaseproof paper. Put 200g  dark chocolate and 175g butter in a heatproof bowl over a saucepan of simmering water ( do not let the base of the bowl touch the water). Leave until melted and smooth.Remove from the heat . Add 325g caster sugar and stir well. Add 130g plain flour and stir well. Finally add 3 beaten eggs and mix well. Spoon the mixture into the baking tray and bake for 30- 35 min ( I usually cook for 25 minute for a lovely gooey texture plus my oven is temperamental !) Very very easy and gorgeous . Enjoy

Taken from ‘The Hummingbird Bakery Cookbook’