In a small pot over medium heat, add in the butter. Stir constantly as the butter browns so that the butter doesn't burn. Remove from heat once the milk solids are golden and the butter is fragrant. Set aside to cool slightly.
In a bowl, add the brown butter, sugars and whisk well. Add in the egg and vanilla extract, mix well again. Add in the flour, bicarbonate soda, baking soda and mix well. Add in the chocolate chunks and mix until the mixture is even.
Divide your cookie dough mixture into 9 even balls and refrigerate for ~15 mins.
Preheat your oven to 180C/350F
Place the cookie balls onto a lined baking sheet, 10cm apart. Bake for 13-15 minutes. Sprinkle with salt flakes immediately out of the oven. Let cookies cool slightly and then serve over ice cream.