1. Heat oven to 300?F. Line 9" x 9" baking pan with foil. Oil and flour the foil. (An 8" x 8" pan can be used. Just bake 5 to 10 additional minutes.) 2. Mix cereal, nuts, fruit, flour, and an extra, if using, in large bowl. 3. Combine sugar and salt in small bowl. Whisk in egg whites and extract, if using. Pour mixture into dry ingredients and stir to combine. 4. Pat into the prepared pan with moist hands or plastic wrap. 5. Bake until bars are dry to the touch, 45 minutes to 1 hour, depending on ingredients used. Cool completely.