Preheat oven to 180ºC In large bowl, blend peanut butter and butter until smooth. Add sugar, eggs and vanilla, beat until creamy. Blend in flour and salt. Stir in 1 cup chips. Spread into ungreased 13x9 inch pan. Bake 25-30 minutes, or until edges begin to brown. Immediately sprinkle remaining chocolate chips on. Let stand 5 minutes until morsels become shiny and soft. Spread evnly over top. Cool completely. cut into 4 cm bars.