Heat oven to 350°F. In bottom of ungreased 10- or 9-inch springform pan, break up cookie dough. With floured fingers, press dough evenly in bottom of pan. Bake 14 to 18 minutes or until golden brown. Cool 15 minutes.
In medium bowl, mix powdered sugar, peanut butter, butter and water until well blended. (If necessary, add additional water 1 teaspoon at a time until mixture is smooth.) Drop spoonfuls of mixture over baked cookie crust; press evenly to cover crust.
Spread melted chocolate chips over peanut butter mixture. If desired, carefully swirl chocolate with fork. Garnish with pecan halves. Refrigerate 1 hour or until chocolate is set.