HEAT morsels and 3/4 cup peanut butter in small, heavy-duty saucepan over low heat, stirring constantly until smooth; remove from heat. Add sugar; stir vigorously until smooth.
PLACE cereal in large bowl. Add 1 cup melted chocolate mixture; stir until evenly coated. Place on ungreased baking sheet. Using small metal spatula, shape into 10-inch circle with slightly raised 1-inch-wide border. Pour remaining chocolate mixture in center of circle; spread to border.
PLACE remaining peanut butter in small, heavy-duty plastic bag. Cut tiny corner from bag; squeeze to pipe concentric circles on top of chocolate. Using wooden pick or tip of sharp knife, pull tip through peanut butter from center to border. Refrigerate for 30 minutes or until firm. Cut into wedges.