Preheat oven to 350°F. Line a 9x13 pan with parchment paper or grease the pan very well with butter. In a medium size saucepan, melt the butter over medium low heat. Remove from the heat and stir in the brown sugar and vanilla until the mixture is smooth. Add the eggs and stir to combine.
In a separate bowl, combine the dry ingredients and then add to the mixture in the saucepan. Stir to combine. Add the chocolate chips and the chopped nuts and stir again to combine. Pour the batter into the prepared pan and bake for 21-23 minutes or until a toothpick inserted comes out with moist crumbs. Let cool completely before slicing into bars, or serve warm topped with vanilla ice cream. Enjoy!