Heat oven to 350°F (325°F for dark or nonstick pan). Line bottom and sides of 13x9-inch pan with foil, leaving 1 inch of foil overhanging at 2 opposite sides of pan; spray foil with cooking spray.
In large microwavable bowl, microwave 3/4 cup butter, 2 tablespoons water and 2/3 cup sugar uncovered on High about 1 minute or until mixture just starts to boil; stir until blended. Stir in 1 cup chocolate chips until melted. Stir in 1 teaspoon vanilla and the eggs until well mixed. Stir in flour and baking powder. In pan, spread batter evenly.
Bake 18 to 23 minutes or until toothpick inserted in center comes out clean (do not overbake). Cool completely in pan on cooling rack, about 30 minutes.
In 2-quart saucepan, heat 1 cup sugar, 1/4 cup butter and the milk to boiling over medium heat, stirring constantly. Boil 5 minutes, stirring constantly. Stir in marshmallow creme, 1/4 cup of the peanut butter and 1/2 teaspoon vanilla. Pour over brownies. Sprinkle peanuts over top.
In 1-quart saucepan, heat caramels and 1/4 cup water over medium-low heat, stirring constantly, until caramels are melted; pour over peanuts.
In medium microwavable bowl, microwave 1 cup chocolate chips and the butterscotch chips uncovered on High about 1 minute or until softened; stir until smooth. Stir in remaining 1/4 cup peanut butter; spread over caramel layer. Refrigerate at least 1 hour before cutting. Use foil to lift brownies from pan before cutting. For brownies, cut into 8 rows by 6 rows. Store in refrigerator.