LINE 13 x 9-inch baking pan with foil leaving an overhang on two sides. Spray foil with nonstick cooking spray.
HEAT marshmallows, butter and salt in large, heavy-duty saucepan over medium-low heat, stirring frequently, for 5 to 10 minutes, until smooth. Remove from heat. Add 1 cup morsels and peanut butter; stir until melted.
WORKING QUICKLY, stir in cereal, chopped Butterfinger and pretzels. Stir in remaining 3/4 cup morsels. Spread mixture into prepared baking pan with greased spatula, pressing down lightly. Cool for 2 hours or until set. Lift from pan; remove foil. Cut into bars with serrated knife.