Preheat oven to 350°F. Butter and flour 8x8x2-inch metal baking pan.
Whisk 1 cup flour, salt,and baking soda in medium bowl to blend.Melt 1/2 cup butter in heavy large saucepanover low heat.
Remove from heat; add sugarand whisk until smooth. Cool mixture 2minutes; whisk in eggs and vanilla. Usingflexible spatula, stir in flour mixture, thenhalf of peanuts and half of chocolate chips.
Spread batter in prepared pan; sprinkle withremaining peanuts and chocolate chips.
Bake blondies until golden, testerinserted into center comes out clean, andedges just begin to pull away from sides ofpan, about 30 minutes; cool completely in panon rack. DO AHEAD: Can be made 2 days ahead.Cover tightly and store at room temperature.