Method

• 1.
  The day before, melt the cold butter in a medium frypan over medium heat. Cook, stirring occasionally, until the butter turns a deep golden brown and develops a nutty aroma. Transfer to a heatproof container. Cool, then store in the fridge. The next day, bring the burnt butter to room temperature.
• 2.
  Preheat oven to 200°C/180°C fan-forced Line 2 large baking trays with baking paper.
• 3.
  Sift the flours and bicarb over a medium bowl, then stir in 1 tsp salt flakes. Set aside.
• 4.
  Using a stand mixer fitted with the paddle attachment, cream the room-temperature butter, brown butter, both sugars and vanilla on medium-high speed for 3 minutes, scraping down side of bowl occasionally, until light and fluffy. Slowly mix in eggs, one at a time. Add flour mixture and mix on low speed for 20 seconds until almost combined, then add the chocolate and mix on low speed for 15-20 seconds until just combined and chocolate is fully distributed.
• 5.
  Place a large piece of baking paper on a work surface, then use a 1/3-cup (80ml) capacity ice cream scoop to drop 22 portions of dough onto paper. Transfer 5-6 rounds of dough onto each prepared tray, leaving 7cm space between each.
• 6.
  Bake for 10 minutes. Remove from oven and gently press each with the base of a small saucepan to flatten. Sprinkle with salt flakes and bake for another 5 minutes until medium golden brown.
• 7.
  Use the baking paper to slide cookies onto wire racks and set aside to cool. The cookies will firm up as they cool but will remain chewy. Repeat process, relining the baking trays with baking paper with each batch, until all cookies have been baked.