Preheat oven to 350° F. Grease 15 1/2" by 10 1/2" jelly-roll pan. On waxed paper, combine flour, baking soda, and 1 teaspoon salt.
In 3- to 4-quart saucepan, melt butter over medium heat. Remove saucepan from heat; stir in sugar and vanilla. Add eggs; stir until well mixed. Stir in flour mixture and add-ins just until blended. Spread batter into prepared pan.
Bake blondie 25 minutes or until toothpick inserted 2 inches from edges comes out almost clean. Do not overbake; blondie will firm as it cools. Cool in pan on wire rack. When cool, cut blondie lengthwise into 4 strips, then cut each strip crosswise into 6 pieces.