Preheat oven to 350 degrees. In large bowl beat peanut butter and butter until smooth. Add sugar, eggs, and vanilla. Beat until creamy. Blend in flour and salt. Stir in 1 cup chocolate chips. Spread in 13 x 9 inch ungreased baking pan. Bake 25 to 30 minutes or until edges brown. Remove from oven. Immediately spread with rest of chocolate chips. After chips melt spread evenly over top. Cool and cut.