Preheat oven to 350 degrees. In large mixer bowl, beat peanut butter and butter until smooth, about 1 minute. Add sugar, eggs and vanilla extract; beat until creamy. Blend in flour and salt. Stir in 1 cup milk chocolate chips. Spread into (ungreased) 13 x 9 inch baking pan.
Bake 25-30 minutes or until edges begin to brown. Immediately sprinkle remaining milk chocolate chips over cookie layer. Let stand 5 minutes or until chocolate chips become shiny and soft. Spread chocolate evenly over top. Cool completely. Cut into bars.