FOR COOKIE BASE:
PREHEAT oven to 350º F.
COMBINE flour, baking soda and salt in small bowl. Beat butter, granulated sugar and brown sugar in large mixer bowl until creamy. Add egg; beat well. Gradually beat in flour mixture. Stir in 3/4 cup morsels. Press dough onto bottom of ungreased 13 x 9-inch baking pan.
BAKE for 16 to 18 minutes or until light golden brown. Immediately sprinkle with remaining morsels. Let stand for 5 minutes or until morsels are shiny; spread. Cool completely in pan on wire rack.
FOR PEANUT BUTTER LAYER:
COMBINE peanut butter and butter in large mixer bowl until well blended. Gradually add powdered sugar and water; beat well. Spread over cookie base.
FOR CHOCOLATE LAYER:
SPREAD melted chocolate over peanut butter layer. Refrigerate about 1 hour or until firm.
SPREAD whipped topping over chocolate layer. Serve immediately or refrigerate.