Preheat oven to 170°C.

Put half the butter (70g) into a small saucepan over a medium heat. As the butter melts, it will begin to foam and turn brown. Once you smell a nutty aroma, take the pan off the heat and transfer the butter into a heat-proof bowl to cool.

Meanwhile, cream the remaining butter and sugars for at least 5 minutes until the mixture becomes light and fluffy.

Add the egg, vanilla extract and cooled brown butter and beat well.

Add choc chips, flour, baking soda, baking powder and sea salt. Beat on low speed until just combined (don't overwork the mixture or it can become tough).

Dollop tablespoon sized balls of cookie dough onto lined baking trays.

Gently flatten each cookie and add an extra sprinkle of sea salt over each cookie.

Bake until cookies are golden around the edges, around 12-14 minutes.