Heat oven to 375. For bars, in large mixer bowl, combine brown sugar, granulated sugar, butter, egg and vanilla. Beat at medium speed, scraping bowl often, until well mixed, 1 to 2 minutes. Add flour, baking soda and salt. Continue beating until well mixed, 1 to 2 minutes. Stir in nuts and chips. Press on bottom of ungreased 15x10x1 inch jelly-roll pan. Bake for 12 to 17 minutes, or until edges are lightly browned.

For topping, in small saucepan, combine chocolate chips and peanut butter. Cook over low heat, stirring constantly, until melted, 4 to 5 minutes. Spread over warm bars. Sprinkle nuts over top. Refrigerate until topping sets, about 1 hour. Cut into bars. Store, covered, at room temperature. Makes about 5 dozen bars.