• Preheat the oven to 180C.

  Prep an 8 inch square pan (preferably a light metallic pan) with parchment paper, pressing the paper firmly against the sides of the pan and leaving a 2-inch overhang. This "parchment sling" makes it easier to remove the brownies from the pan once baked. Grease the parchment paper and set aside.

Brown the butter

• Melt the butter in a saucepan set over medium low heat, stirring the butter around the pan to ensure that it melts evenly. You will start to see it foaming and sizzling around the edges; continue cooking (swirling occasionally) until the butter develops a nutty aroma and shifts to a toasty brown colour.
• Once you can see amber-brown specks at the bottom of the pan, remove from heat and pour out the brown butter into a heat-proof mixing bowl (don't forget to scape out those browned bits too!). Quickly add in the chopped chocolate, whisking until the chocolate has melted.
  

Prepare the batter

• In another bowl, vigorously beat the eggs, sugar and vanilla extract together with a hand mixer (on medium high speed) until the mixture develops a thick and fluffy (almost foamy) texture and a pale colour. This step is crucial if you want a tissue-thin crust on the top of your brownies.
• Next, beat in the melted chocolate and brown butter mixture on medium low speed.
  
• Sift in the dry ingredients (cocoa powder, flour, instant coffee and salt) and then beat vigorously with a hand mixer (or with at least 60 strokes of a wooden spoon/ spatula) until the brownie batter has come together with a thick and shiny consistency.
• Gently fold in the chopped walnuts and transfer the batter to a pan, smoothening out the surface.
  
• Bake for 17 - 20 minutes until the brownies are set but a toothpick plunged in the centre comes out slightly dirty with a few moist crumbs attached. Don't over-bake if you want a gooey texture!
• Let the brownies cool down completely on a wire rack, before removing from the pan and slicing. Store in an airtight container.