1Heat oven to 350°F. Spray 13x9-inch pan with cooking spray. In large bowl, beat sugar, butter and peanut butter until light and fluffy. Add milk, vanilla and egg; beat until well blended. Add flour, baking soda and salt; mix well. Spread in pan.
2Bake 19 to 24 minutes or until edges are golden brown. Immediately sprinkle with chocolate chips; let stand 5 minutes.
3Using metal spatula, spread softened chips to frost bars. Sprinkle with peanuts. Cool completely in pan on cooling rack, about 2 hours. For bars, cut into 6 rows by 6 rows.