Preheat oven to 170°C /fan oven 150°C, 325°F, Gas Mark 3
Butter and baseline a Pyrex Non-Stick 19x26cm Baking tin with baking parchment.
Place the chocolate and butter in a bowl over a pan of simmering water. Do not let the water touch the bottom of the bowl. Heat the gently until the butter and chocolate is melted. Remove the bowl from the pan.
Add the sugar to the chocolate mixture and beat. Whisk in the eggs using a Kenwood Hand Mixer one at a time, until combined.
Add sifted flour and beat until smooth. Fold in the fudge chunks and chocolate chips. Pour into the prepared tin and bake for 45 minutes or until the surface has set but still feels squidgy underneath. Leave to cool completely and cut into bite sized pieces.