Add brown sugar to the beaten eggs and beat again.
Add oil and vanilla and beat well.
Add flour, salt, and baking powder, mix well. Mixture will be thick.
Stir in butterscotch chips and pecans, if using.
Spray 9x13 pan with nonstick spray, and spread batter into pan. Spread the batter evenly into all corners.
Bake at 350 for 15-20 minutes, or until edges are golden brown and center starts to fall flat. Remove from oven and cool before eating.
Notes
You can substitute chocolate chips or white chips, if desired. Pecans are a wonderful addition, I also use sliced almonds or walnuts too. Take them out as soon as they start to sink, for gooey squares, or wait till they have fallen flat and bake a bit longer for chewy bars. The center will be more gooey and the edges will get more chewy.