Butter and icing sugar to line the tin and prevent sticking
100gmilk chocolate and 100g white chocolate for decorating if desired
Pre heat the oven to 180 degrees C (fan). Butter the baking tin and dust with icing sugar, this will prevent the brownie from sticking during baking.
Cut up the butter into chunks and add to a microwavable bowl, along with the 280g of chocolate chips. Microwave in 20 second bursts, stirring in between until fully melted. (NB: with the butter mixed in, this won't take long to melt at all).
Place the melted chocolate and butter to one side.
In a mixing bowl whisk together the sugar and eggs. The mix of sugar and eggs is known as a sabayon. However, to achieve a good sabayon there is no room for gentle mixing: get your muscles out and whisk well until the mixture goes paler and begins to ribbon with the movement of the whisk.
Pour the melted chocolate and butter into the sabayon and stir in well. Then sieve in the flour and cocoa powder and use a spatula to gently fold in. It will appear quite dry at first, but keep folding and eventually the mixture will come together. Finally add the hazelnuts and white chocolate, and fold in again, before gently transferring to the prepared baking tin. use a knife or spatula to spread the mixture evenly in the tin.
Pop in the oven for 30 minutes, then check by inserting a skewer into the centre of the cake. If the skewer comes out gooey then put back in for a further 5 minutes. Check again and return to the oven if required, do not bake past 45 minutes as the edges of the brownie will begin to burn.
Once fully baked, leave on the side, in the tin, to completely cool. This usually takes 1-2 hours.
Only remove from the tin once you are satisfied that the brownie is complete cooled.
To remove, run a knife around the edge of the tin, then place a board over the top of the tin and gently turn over to release the brownie.
Cut up the slab into suitably sized square pieces: I usually cut off the edges first to remove any charring and to neaten up. Then divide into 20-25 small squares.
If you would like to decorate the brownies as in the pictures:
Melt 100g of white chocolate in the microwave (20 second bursts), then transfer to a piping bag, snip off the end and roughly pipe chocolate zig zags over each brownie. Repeat this with milk chocolate, then leave on the side to fully set.