Pre heat oven to 150°C/ 300°F or 130°C fan
Spray a 20cm (8 inch) square pan with cooking spray and line it with baking paper. Set aside.
Add the butter to a medium saucepan and set it over medium heat to brown the butter, stirring occasionally. This will take between 5-8 minutes. It will bubble, crackle and pop, then go golden brown. Once browned, loosen the browned bits from the bottom and stir them through with a silicone spatula.
Add the 75g of chopped dark chocolate, along with the espresso. The mixture will bubble up quite a bit -just give it a good stir, then set aside to cool a little. You can place it in the fridge to cool down faster.
In a small bowl, whisk together the flour, cocoa and salt, then stir through the extra chocolate chips. Set aside.
In the bowl of your stand mixer fitted with a whisk attachment, whisk the eggs, sugars and vanilla at a medium speed, until light and fluffy (4-5 minutes).
Add the cooled chocolate and browned butter mixture and combine, using a silicone spatula. Make sure you really scrape the sides of the bowl.
Fold through the dry ingredients until just combined.
Bake for 35 minutes, until the edges are slightly crispy, but the centre is still a little gooey. The brownie will continue to cook as it cools in the pan.
Remove the brownie from the oven and allow it to cool completely before slicing into bars or squares.
Serve dusted with icing sugar, or topped with either store bought ice cream or my Vanilla Bean Ice Cream or Chantilly Cream