Ingredients
250g unsalted butter, diced, plus extra for greasing 
250g dark chocolate, roughly chopped 
6 large eggs 
50g caster sugar 
165g light brown sugar 
2 tbsp Frangelico (optional) 
¼ tsp fine sea salt 
85g roasted hazelnuts, finely chopped 

For the meringue topping 
3 large egg whites 
200g caster sugar 
2 tbsp cocoa powder

* for a mocha version add 1 tbsp of instant espresso powder

Method
Preheat the oven to 180c and grease and line a 23 x 33cm baking tin. 

Put the butter and chocolate into a microwaveable bowl and melt in a microwave on 30 second bursts until the butter and chocolate are melted and one. Put to one side. 

Place the eggs, both sugars and the salt into a stand mixer and whisk on a medium-high speed until pale and tripled in volume. If you do not have a stand mixer and only have electric hand mixers then this will take 8-10 minutes. 

Take a couple of tbsps of hazelnuts out and gently fold the rest through the egg mixture.  Pour ⅓ of the chocolate in to the egg mixture along with the frangelico if using and fold through and repeat, ensuring each addition has thoroughly folded through before adding the next third.  Pour into the tin and shake to level off.  Bake for half an hour. 

After 20 mins, make the meringue topping. Place the egg whites and a pinch of salt into a stand mixer and whisk until the egg whites are at foamy soft peaks.  Slowly add the sugar a tbsp at a time and continue to whisk until you have glossy, stiff peaks. 

Take the chocolate brownie out of the oven and very carefully add 1 tbsp of meringue at a time to the top, you need to do this slowly and carefully so it does not sink. It needs to cover the top.  Dust the top of the meringue with the cocoa and with the back of a spoon, gently swirl so your meringue is marbled.  Top with the reserved hazelnuts and put back into the oven for a further 25 minutes. 

Remove from the oven and leave in the tin to cool. When totally cool, cut into 12 and try not to eat in one sitting. 

- Original recipe by Edd Kimber, One Tin Bakes 

Note

To make a mocha version, reduce the cocoa in the meringue by half and replace with 1 tbsp of instant espresso powder.