1. Preheat oven to 350°.
2. Weigh or lightly spoon flour into a dry measuring cup; level with a knife. Combine flour and next 5 ingredients in a large bowl; stir with a whisk. Combine oil, vanilla, and egg whites in a small bowl, stirring with a whisk; add to flour mixture, stirring just until moist. Lightly coat hands with cooking spray. Press batter into an 8inch square metal baking pan coated with cooking spray.
3. Bake at 350° for 18 minutes or until a wooden pick inserted in center comes out clean. Cool in pan on a wire rack. Sift powdered sugar over top. Cut into bars.
Young Chefs can:
Crush graham crackers in a sealed plastic bag
Measure butterscotch morsels
Older Chefs can:
Stir together dry ingredients
Press batter into baking pan