Pre-heat oven to 160'C (140" fan-forced). Grease and line 20x30cm tin
Melt butter over medium heat. Remove from heat, add chocolate melts and stir until combined/melted
gently fold melted chocolate into egg mixture
Fold in sifted flour and cocoa (works just as well if you are lazy like me, and you do not sift!)
Fold in chocolate chunks and walnuts
Pour into prepared tray and bake for 50mins
The crust will be delicate, and the 'cake' dense and moist
Leave to cool in pan before cutting!