No Bake Chocolate Peanut Butter Bars

2 cups peanut butter, divided use
3/4 cup butter or margarine
2 cups powdered sugar
3 cups graham cracker crumbs
2 cups semisweet chocolate chips

1. Beat 1 1/4 cups peanut butter and butter in large mixer bowl until creamy. Gradually beat in 1 cup powdered sugar. With hands or wooden spoon, work in remaining powdered sugar, graham cracker crumbs and 1/2 cup chocolate chips. Press evenly into greased 13 x 9-inch baking pan. Smooth top with spatula.
2. Melt remaining peanut butter and remaining chocolate chips in medium, heavy-duty saucepan over lowest possible heat, stirring constantly, until smooth. Spread over graham cracker crust in pan. Chill for at least 1 hour or until chocolate is firm; cut into bars. Store in refrigerator.