Place the butter in a saucepan and cook for about 5-10min until the butter has browned and created a slightly nutty scent.
Preheat the oven to 180ºC/350ºF and spray your skillet with non-stick spray.
In a mixing bowl combine all the dry ingredients (except the chocolate).
Using an electric mixer, mix together the browned butter and both sugars then add the eggs and vanilla and continue to mix.
Add the dry ingredients to the butter mixture and mix until just combined.
Fold the chocolate chunks and walnuts into the mixture.
Spread the batter into the skillet and bake for 15-20 minutes for a chewy cookie.
Serve with walnuts and ice cream.