Begin by heating you butter on a medium heat swirling constantly, it will go through various stages. At first the butter will melt, then it will begin to boil and the final stage is when it foams. This is indicative of the brown butter being ready, this whole process should take about 6 minutes.
Pour the butter into a large bowl and add the egg, vanilla extract and sugar. Whisk until combined.
Add the remaining dry ingredients and stir until a sticky batter forms.
Add in the chocolate an dmix until combined, be careful not to over-mix!
Mould the batter into 10 equal balls and put on two baking trays lined with parchment paper, ensure that stye are venally spaced and have room to spread on the oven. Refrigerate them for 45 minutes.
Preheat the oven to 180° once the cookie shave chilled for 35 minutes.
Put the chilled cookies in the oven to the bake for around 18 minutes. Halfway through remove the trays and bang on the counter a couple fo times, this allows the cookies to form their characteristic cracks.
Once baked, sprinkle on some flakey salt and allow them to sit for 5 minutes before enjoying!