Mars Bar Squares

4 Mars bars, cut up
1/2 cup butter or margarine
3 cups Rice Krispies

Heat candy bars and margarine in a large saucepan, stirring often, until melted. Remove from heat. Add cereal; stir to coat. Pack into a greased 9x9 inch pan

Topping:
1 cup semi-sweet chocolate chips
1/4 cup butter or margarine

Combine in a saucepan on low heat, stirring often until smooth. Spread over squares. Put in the fridge to cool. Cut into 36 squares.