In a small bowl, mix flour, baking powder and salt. In a 1-qt. glass jar, layer flour mixture, pecans, brown sugar and butterscotch chips. Cover and store in a cool, dry place up to 3 months. Yield: 1 batch (about 4 cups mix)., To prepare brownies: Preheat oven to 350°. In a large saucepan, heat butter over medium heat until just melted. Remove from heat. Whisk in eggs and vanilla until blended. Gradually add brownie mix, mixing well. Spread into a greased 13x9-in. baking pan., Bake 20-25 minutes or until a toothpick inserted in center comes out with moist crumbs (do not overbake). Cool completely in pan on a wire rack.