Preheat oven to 350oF and grease a 9 x 13-inch baking pan.
Combine dry ingredients in a mixing bowl. Whisk together wet ingredients and fold into the dry ingredients. If desired, add half the chocolate chips and chopped walnuts to the mix. Pour mixture into the prepared pan and sprinkle with remaining chocolate chips and walnuts, if using.
For fudge-like brownies, bake for 20-25 minutes. For cake-like brownies, bake 25-30 minutes. Let the brownies cool slightly before serving.