Line an 8x8-inch baking pan with parchment paper. Set aside.
Combine half (about 1 cup) of the chocolate chips and 1 tablespoon butter in a microwave-safe bowl. Microwave on High, stirring in 30-second intervals, until melted and smooth, about 75 seconds. Stir in 1 cup rice cereal and spread in an even layer in the prepared baking pan. Refrigerate, uncovered, until firm, about 5 minutes. Reserve bowl.
While chocolate layer cools, place dulce de leche and 2 tablespoons butter in a separate microwave-safe bowl. Microwave on HIGH, stirring after 30 seconds, until melted, smooth, and spreadable, about 1 minute.
Carefully transfer dulce de leche to the chilled chocolate layer and spread into an even layer, leaving a ½-inch border around the edges. Return to the refrigerator to chill until firm, 5 to 10 minutes.
Combine remaining chocolate chips and 1 tablespoon butter in reserved bowl. Microwave on High, stirring in 30-second intervals, until melted and smooth, 1 ½ to 2 minutes. Stir in remaining 1 cup rice cereal; evenly spread mixture carefully over chilled dulce de leche layer, all the way to the edges of the pan. Refrigerate, uncovered, until completely firm, about 1 hour. Cut into 12 (1 ¼x3 ¾-inch) rectangles. Recipe developed by Julia Levy
