In a 6-qt. stockpot, melt butter over medium heat. Add marshmallows; cook and stir until melted. Remove from heat. Stir in cereal and crushed crackers. Fold in chocolate chips. Press into a greased 13x9-in. baking pan. Cool to room temperature.
For frosting, in a small bowl, beat butter and confectioners' sugar until smooth. Beat in marshmallow creme on low speed just until blended. Spread over bars. Sprinkle crushed crackers over frosting. Cut into bars. Break each candy bar into 12 pieces; place a piece on each bar.