Brown the butter on a medium heat, stirring until it foams and turns golden brown. Remove from the heat and allow to cool down slightly.

In a large bowl, combine the butter with brown and white sugar. Beat together, then add the egg, egg yolk, and vanilla, mixing well.

Sift in the flour and baking soda and add in the salt. Add in the chocolate chips and mix until combined.

Scoop 50g dough into balls and place them on a lined baking tray. Refrigerate the dough for at least 30 minutes, or overnight.

Preheat the oven to 180°C (350°F) and bake for 11 minutes, until edges are golden and centres are still soft.

Allow the cookies to cool before serving.