2In a medium saucepan, stir together sugar, evaporated milk and margarine (or butter); bring to a boil over high heat. Reduce heat to medium-low and cook, stirring constantly, about 3 minutes.
Stir in chocolate and marshmallows; remove pan from heat and stir until smooth.
3Pour mixture into prepared pan and refrigerate until firm, about 2 hours. Cut into thirty-six 1 1/3-inch squares and serve. Recipe makes 36 pieces.