Step 1

Preheat the oven to 160°C/fan140°C/gas Grease and line the base and 2 sides of a 20cm square cake tin with 1 piece of baking paper (this makes the brownie easy to lift out of the cake tin).

Step 2

Place the chocolate and butter in a large heatproof bowl set over a pan of gently simmering water (don’t let the bowl touch the water) and heat, stirring occasionally, until melted (see How To… in the Know How section of the website). Remove the bowl from the pan and cool slightly.

Step 3

Using electric beaters, beat the caster sugar and vanilla into the chocolate mixture. Whisk in the eggs, 1 at a time, until the mixture is well combined, then add the sifted plain flour and beat until the mixture is smooth. Stir in the white and milk chocolate chunks.

Step 4

Pour the mixture into the lined tin and bake in the oven for 30 minutes or until a skewer inserted into the centre of the brownie comes out with a few moist crumbs.

Step 5

Allow to cool completely in the tin before removing the brownie from the tin using the paper as handles. Cut into 20 squares and serve dusted with cocoa powder.