Lightly grease a 9 x 13-inch pan and preheat your oven to 350°F. Melt the butter in a medium-sized saucepan. Add the brown sugar, and stir until the mixture is smooth.
Remove the pan from the heat, pour the butter-sugar mixture into a medium-sized bowl, and allow it to cool to lukewarm. Whisk in the eggs one at a time. Stir in the vanilla extract and salt.
Whisk the flours and baking powder together, then add the dry ingredients to the sugar mixture, stirring to combine. Finally, fold in the chips and nuts.
Spread the mixture evenly in the pan, and bake the brownies for 30 to 35 minutes, until they're light brown on the edges and top.