Preheat oven to 350F°. In a stand mixer or large bowl, cream butter and brown sugar. Add your eggs and vanilla, blending well and scraping sides as needed. Mix in remaining dry ingredients. When you have a nice smooth batter, add in your chocolate chips and nuts. Transfer to a greased 13x9" baking pan. Cook for 30 minutes or until a toothpick comes out clean.
Cool completely before cutting. You may want to dive right in but it won't cut well. Been there done that, but sometimes it's just too hard to resist. If you want nice smooth cuts and solid pieces, wait.