Butter 15-1/2x10-1/2x1 inch jelly roll pan. sprinkle 1 cup peanut butter chips evenly onto bottom of prepared pan, set aside.
Melt butter in heavy 2-1/2-quart saucepan, stir in sugar, corn syrup and water. Cook over medium heat, stirring constantly until mixture reaches 300 degrees on candy thermometer, this should take 30 to 35 min.
Remove from heat. immediately spread mixture in prepared pan, sprinkle with remaining 2/3 c. peanut butter chips. Cool completely. Remove from pan. Break into pieces. Store in container.