Preheat oven to 325 degrees F.
In a 9 inch cast iron skillet, melt the butter over medium heat, swirling or stirring gently. It will crackle, foam and eventually start to brown. Allow it to brown just until it is fragrant, then remove from heat and carefully (use your best oven mitt!) pour into a mixing bowl, leaving a thin coating of residual butter in skillet. Whisk or just stir in the sugar, cocoa powder, 2 teaspoons water, vanilla and ¼ teaspoon salt.
Let the mixture cool for about 5 minutes. It will still be hot. Add eggs to hot mixture 1 at a time, beating well after each egg is added. Add flour and stir until blended. Beat or whisk 60 strokes. Stir in nuts. At this point batter should be just slightly warm, but not so warm it will melt the chocolate chips. Stir in ½ cup of chocolate chips and scrape batter into the cast iron skillet.
Bake brownies for 25 minutes. They should appear shiny and set. Let cool completely, then cut into wedges and gently pry from the skillet.