In a medium saucepan combine the sugar, evaporated milk and butter.
Heat on medium-high until mixture comes to a boil.
Reduce heat to medium and cook for 5 minutes.
Remove from heat.
Stir in marshmallow creme and peanut butter.
Add Rice Krispies.
Pour marshmallow mixture over cooled brownies.
Spread to edges.
Place pan in freezer for at least an hour.