Double chocolate brownies
Preheat the oven to 180C/170C fan/Gas 4.
Line the sides and base of a 33x23x5.5cm/13x9x2in baking tin with baking paper.
Place the butter and chocolate into a heatproof bowl. Place the bowl over a saucepan of barely simmering water (do not let the base of the bowl touch the simmering water) and allow to melt.
Put the eggs, sugar and vanilla extract in a clean bowl and whisk together.
Once the chocolate and butter have melted, set aside and allow to cool slightly. Add the egg mixture and whisk to combine.
Sift the flour and salt together then fold into the chocolate mixture. Add the white chocolate pieces and mix to combine.
Pour the mixture into the baking tin and bake for 25 minutes. Remove from the oven and allow to cool a little in the tin.
To serve, remove from the baking tin and cut into squares while still warm. Sprinkle with icing sugar, if using.