1. Heat oven to 350°F. Grease 13x9x2-inch baking pan.
2. Beat butter, granulated sugar, brown sugar, eggs and vanilla in large bowl until fluffy. Stir together flour, baking soda and salt; add to butter mixture, blending well. Stir in peanut butter chips. Spread batter into prepared pan.
3. Bake 30 to 35 minutes or until golden. Shortly before end of baking time, melt chocolate chips with sweetened condensed milk in heavy saucepan over low heat, stirring constantly until chips are melted. Remove from heat; stir in remaining 1/2 teaspoon vanilla. Spread evenly over baked blondies. Sprinkle with peanuts; press down lightly. Cool.
4. Refrigerate about 3 hours or until firm. Cut into bars. Store covered at room temperature. About 24 blondies.