Line an 8-inch square baking pan with parchment paper. In a medium saucepan, melt half of the chocolate and 1 tablespoon butter over low heat. Remove from the heat; stir in 1 cup peanut butter, then 2 cups rice cereal. Spread the mixture evenly in the prepared pan; refrigerate until set, about 15 minutes. Wash out the saucepan.
In the saucepan, combine the remaining 2 sticks butter and the salt; melt over medium heat, stirring. Remove from the heat and stir in the remaining peanut butter and the confectioners' sugar. Spread half of the peanut butter mixture over the cereal layer. Top with the remaining 1 cup cereal.
In a small bowl, microwave the remaining chocolate at medium power until melted, 1 1/2 minutes. Stir into the remaining peanut butter mixture. Spread evenly on the cereal-topped peanut butter layer; refrigerate until set, about 45 minutes. Cut into 16 pieces.