Place margarine, peanut butter and marshmallow in a microwave-safe bowl and microwave them one minute and then stir, microwave another minute and stir until smooth.
Stir in the crispy rice cereal and mix well.
Press into the greased pan. I find that it is easier to press the mixture into the pan if I first spray my hands with non-stick spray and use my hands.
Place the chocolate chips in another microwave safe bowl and microwave for one minute then stir. Microwave 30 seconds then stir. Continue the 30 second and stirring intervals until the chocolate chips are melted and smooth.
Spread on top of the Rice Krispie treats and then set aside to cool. I placed mine in the refrigerator to help speed up the process.