For the brown butter streusel:

1. Place the butter into a small saucepan set over medium heat. Heat, stirring often, until the butter is golden and melted. Increase the heat to medium-high and continue to cook, swirling the pan occasionally but not stirring, until the butter is beginning to turn amber in colour and smells nutty in fragrance. The butter will begin to foam, but will subside as it continues to cook. Some brown butter solids should just be beginning to form at the base of the saucepan. Remove from the heat and set aside to cool slightly.
2. Place the roughly crushed graham cracker crumbs in a small bowl. Stir in the sugar and fleur de sel. Pour in the brown butter and mix until the crumbs are evenly moistened. Set aside.

For the brownie:

1. Pre-heat the oven to 175 c. Grease and line a 32 x 22 cm rectangular baking tin with non-stick parchment paper. Lightly grease the parchment and let the paper slightly overhang the sides. Set aside.
2. Place the butter into a medium sized saucepan set over medium heat. Heat, stirring often, until the butter is golden and melted. Then, pour the melted butter into a large sized mixing bowl. Add in the granulated sugar. Whisk, until combined. Add in the eggs, one at a time, whisking until smooth and glossy. Add in the vanilla bean extract and espresso. Whisk until incorporated.
3. Sift over the dutch processed cocoa powder, flour and salt. Use a rubber spatula or wooden spoon to fold the dry ingredients into the mixture until smooth and well combined.
4. Pour the brownie batter into the prepared baking tin. Use a spatula to spread the mixture to the edges of the pan. Smooth out the top then roughly scatter over the brown butter streusel. Bake, for 16 to 19 minutes, or until the edges are firm and the middle is puffed and set but still remains slightly soft in the center. The streusel should also be deeply toasted. Remove from the oven and set the brownie aside to cool completely.

For the fleur de sel ganache:

1. Click the link above for the recipe

For the meringue:

1. In the bowl of a stand mixer, stir the egg whites and sugar together to combine. Set the bowl over a saucepan filled with about 2.5 cm’s of water and over medium-low heat. Do not let the base of the bowl touch the water. Heat the mixture, until it reaches about 70 Celsius on a candy thermometer. Make sure to whisk the mixture with a fork often and scrape down the bottom and sides of the bowl to avoid any sugar crystallization.
2. Once at temperature, remove the bowl from the heat and place it in the stand mixer fitted with the whisk attachment. Set the mixer speed to medium-high. Whisk, until the mixture forms that of stiff and glossy peaks, about 6 minutes. Add in the vanilla bean seeds and continue to whisk until evenly combined. The bowl should be cool to the touch and all the steam will have escaped from the meringue. Stop mixing and remove the bowl from the stand mixer.
3. Carefully turn the brownie out and onto a serving plate or tray. Use the back of a metal spoon to spread the meringue over the top of the set ganache, in a swoop-and-swirl motion, to get those meringue peaks. Use a kitchen blow torch to char the top of the meringue until it is evenly toasted. Make sure to keep the kitchen torch as far away from the ganache layer as possible so that it doesn’t melt. When you’re ready to serve, sprinkle over a little extra fleur de sel or flaked salt over the top of the brownie, before slicing. Serve at room temperature. The brownie will keep for up to 3 days, stored in an air-tight container, in a dark-cool place.