Beat 1 ¼ cups peanut butter and butter in larger mixer bowl until creamy. Gradually beat in 1 cup powdered sugar. With hands or wooden spoon, work in remaining 1 cup powdered sugar, graham cracker crumbs and ½ cup choc chips. Press evenly into greased baking pan. Smooth top with spatula.
Melt remaining ¾ cup peanut butter and remaining 1 ½ cup chips in medium heavy duty saucepan over lowest possible heat, stirring constantly until smooth. Spread over graham cracker crust in pan.
Refrigerate for at least 1 hour until chocolate is firm. Cut into bars. Store in covered container in refrigerator.